Fix all Doxygen errors and make any future errors fatal (#118) ...

* Start working on fixing doxygen warnings

* Upgrade doxyfile to Doxygen 1.9.1

* Clean up some unmatched groups and add some exclusions

* Fix docs for rtos::ThisThread not showing up

* Fix up KV store docs

* Fix incorrect @files, some more incorrect groups

* Fix lots of broken links

* Start fixing mbedtls groups

* Fix more mbedtls docs

* Fix remaining mbedtls files with missing or incorrect grouping

* Fix a huge amount of PSA docs errors

* Fix a few more mbedtls docs errors

* Fix __cplusplus not defined for docs, clean up call in callback typedef, fix some docs errors

* Fix some broken doc links in HAL headers

* Fix more PSA doc errors

* Fix some doxygen errors in networking code

* Fix lots of network related doc errors

* Try and fix some CI failures

* Use Doxygen Action instead of doxygen in Mbed container to get the right version

* Try removing docs check

* Add first part of doxygen action

* Add next part of doxygen action

* Fix yaml syntax error

* Add in license check fix

* Try using verbose scancode

* Fix some more docs issues, workaround scancode-toolkit#3179

* Clean up the LoRaRadio get_state() function on each implementation.  Also fix some other compile and doc errors.

* Fix all remaining doxygen errors

* Fix escaping, for realsies this time

* Remove Doxygen unsupported config options, fix some more get_status() declarations

* Fix some UNITTESTS build errors

* Fix one more compile error

* Another unittest error

Move unit test to match file

Convert emac, cellular, and wifi targets, and enable one UDP test

connectivity tests: avoid crash with null pointer

connectivity-netsocket-tests-tests-network-wifi update2 ...

- add minor print to make debug easier
- remove not useful part

connectivity-netsocket-tests-tests-network-wifi update ...

Use default NSAPI configuration

Removing FIXME comment and adding empty line in the test file

Code improvements for the unresolved comments ...

This patch contains improvements mentioned in the unresolved PR
comments:
- function names were changed from socket_sendmsg/socket_recvmsg to
  socket_sendto_control/socket_recvfrom_control.
- default implementation of this functions was provided in the
  NetworkStack class.
- MsgHeaderIterator accesses elements on the aligned addresses.

New feature: send/recv message implementation added to network stack

Unit tests: Remove mbed.h stub from target_h ...

The header `mbed.h` is a convenient wrapper that pre-includes some
platform headers, for use by user applications. Libraries and tests
internal to Mbed OS should not use it, and they should explicitly
include headers they need. So a stub is not needed.

CMake: unittests: Show all tests in CTest report ...

Previously a test executable was recognised as a single test by CTest.
However, test executables usually contain multiple test cases, the
results of the test cases should be individually reported. With our
previous setup we could miss test case failures that didn't cause the
executable to return an error code.

This commit uses gtest_discover_test to discover all test cases in a
test executable. This enables CTest to match test passes and failures
from the googletest binary output.

Unittests: Make netsocket test header dependencies explicit ...

The CMake target `mbed-headers` brings in all
headers, and we are gradually moving away from it and explicitly use
only headers needed by each unit test.

Unittests: Replace files with stubs in netsocket unit tests ...

Some netsocket unit tests depend on nanostack-libservice library, but
should use stubs instead of including the source files. We remove the
source files and link to mbed-stubs-nanostack-libservice.

Unittests: Clean up unused sources from netsocket ...

Some source files included when building netsocket unit tests with CMake
were determined to be unused by removing the files from target_sources()
and verifying that the tests still built and ran successfully. These
files have been removed from CMake builds.

Unittests: connectivity: remove trailing whitespace

CMake: Add mbed-headers-nanostack-libservice library ...

Previously all nanostack libservice headers part of
mbed-headers-connectivity. This PR moves all the nanostack
libservice headers into newly added mbed-headers-nanostack-libraries.
This makes the nanostack libservice stubs more self-contained and
improves the composition of the library.

CMake: Update netsocket, lorawan unittest to use mbed-stubs-mbedtls ...

Update netsocket and lorawan unit tests to link with a mbed-stubs-mbedtls
library that it depends on instead of link with mbed-stubs
which is a group of stubs libraries.

CMake: Move mbedtls stubs to the mbedtls dir ...

Move the connectivity mbedtls stubs into the connectivity/mbedtls
component directory. So we can avoid duplicating the mbed-os source
tree in a central UNITTESTS folder.

CMake: Remove mbed-stubs-rtos-headers library ...

- Previous changes moved all rtos stubs headers into mbed-stubs-rtos-headers
lib, but the decision to keep all stubs headers under the respective
component stubs library so moved all stubs rtos headers under
mbed-stubs-rtos and updated it depend component CMake
- Remove unnecessary add_definition call for UNITTEST as any of the stubs library
added from UNITTEST/CMakeLists.txt is not required this macro

CMake: Move netsocket stub headers to the netsocket doubles dir ...

Previously all the netsocket stubs headers under mbed-stubs-headers,
so this PR move all netsocket stubs headers under
netsocket/tests/UNITTESTS/double directory and update CMake to include
stubs headers into mbed-stubs-netsocket library to make netsocket stubs
to be self-contained.

CMake: Add mbed-headers-netsocket headers library ...

- Previously, all netsocket headers made as a part of the
mbed-headers-connectivity library. To make it easier to separate all
the netsocket headers into the separate mbed-headers-netsocket library
and keep them, as part of netsocket stubs CMake. This makes the
netsocket stubs more self-contained and improves the composition of the library.
- Update cellular, netsocket unit tests to link only with a mbed-headers-netsocket
library that it depends on instead of link with mbed-headers
which is a group of headers libraries.

CMake: Update netsocket, cellular unittest to use mbed-stubs-netsocket ...

Update netsocket and cellular unit tests to link with a mbed-stubs-netsocket
library that it depends on instead of link with mbed-stubs
which is a group of stubs libraries.

CMake: Move netsocket stubs to the netsocket dir ...

Move the connectivity netsocket stubs into the connectivity/netsocket
component directory. So we can avoid duplicating the mbed-os source
tree in a central UNITTESTS folder.

CMake: unit-tests: Add mbed-headers-cellular headers library ...

- Previously all cellular header made as a part of the
mbed-headers-connectivity library. To make it easier to separate all
the cellular headers into the separate mbed-headers-cellular library
and keep them as part of cellular stub CMake. This makes the cellular
stubs more self-contained and improves the composition of the library.
- Update all unit test that depends on cellular headers with mbed-headers-cellular library

CMake: Move connectivity/cellular stubs to the mbed-os/connectivity/cellular dir ...

Move the connectivity cellular into the connectivity/cellular component
directory. So we can avoid duplicating the mbed-os source tree in a
central UNITTESTS folder.

Merge pull request #14828 from hazzlim/add-cmake-supports-psa-tests ...

CMake: Add CMake to mbed-psa greentea tests

CMake: Require TEST_SOURCES in greentea CMake file ...

Assumption that greentea test file is always named main.cpp is
incorrect. Updated mbed_greentea_add_test() macro to make TEST_SOURCES
parameter compulsory, which is used to specify greentea test
file(s). This allows tests to use C, or have a different name.
Therefore also updated all pre-existing greentea test CMake files to
explicity add main.cpp to TEST_SOURCES.

Cellular: Add AT handler buffer size to configuration

CMake: Remove all unittest.cmake script from test suite ...

- Remove redundant cmake script as already added the CMake configuration file
- Remove redundant empty_baseline as it is no longer needed with the help of CMake configuration file

Fix missing newline