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

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

CMake: Update mbed os, unittest CMake and add CMAKE_CROSSCOMPILING guard ...

- Add a new MbedOS project in mbed os root CMake which can be used along with
  BUILD_TESTING conditional check for enabling the unittest build
- Update UNITTEST CMake for setting the CMake configuration like c, cxx flags etc.,
- Add if CMAKE_CROSSCOMPILING conditional check wherever target configuration check
  and toolchain configuration to avoid such configuration gets included for unittest build.

Wiced: remove empty spaces

WicedInterface: fix styling

Update WicedInterface.h ...

Fix the styling error

WICED: Move directory to WiFi driver ...

WICED is something is build to Cypress WiFi on multiple devices, it's a binary form. It is owned
by Seeed studio