Rename inconsistently named testing-related variables. Also fix STM32CUBE not working from application code.

Change google test git tag to main ...

google test changed from master to main branch

Unit tests: Remove redundant CMake target mbed-headers-base ...

Individual libraries' `target_h` stub headers have now all been moved
from `mbed-headers-base` to `mbed-headers-<library>`.

Note: Even though headers previously in `target_h` are technically
stubs/fakes too, they are used by not only unit tests but also regular
libraries when compiled for unit tests, because no target-specific HAL
implementation exists in this case. In order for regular library
sources to pick up `target_h` headers, those headers must

* have the same names as regular headers
* appear first in include paths

This is why those headers are part of `mbed-headers-<library>` and not
`mbed-stubs-<library>`. Before this refactoring, `mbed-headers-base`
was the first in unit tests' include paths.

Unit tests: Move hal target_h stubs ...

Stubs previously in UNITTESTS/target_h/ have the same names as
regular Mbed OS headers, intending to override the latter directly.
We move hal target_h stubs into hal/tests/UNITTESTS/doubles/.

Note: In Mbed OS, the standard include format requires each header to
be prefixed with its module name, for example "hal/gpio_api.h". This
requires headers to be organized in a module directory. But unit tests
stubs for hal correspond to what a real Mbed target would have
implemented (in a non-test scenario), and targets do not currently put
headers in hal/, so we similary put stub headers directly in
hal/tests/UNITTESTS/doubles/ instead of add a hal/ subdirectory there.

Unit tests: Move randLIB.h ...

The stub header randLIB.h overrides the header of the same name in
platform/randlib/ which is an external repository vendored into
the mbed-os codebase. As the repository is synchronized regularly,
it is better not to put overrides there, so we put the randLIB.h
stub into the regular platform doubles directory.

Unit tests: Move drivers target_h stubs

Unit tests: Move rtos target_h stubs

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.

Unit tests: Move platform target_h stubs ...

Stubs previously in UNITTESTS/target_h/ have the same names as
regular Mbed OS headers, intending to override the latter directly.
We move platform target_h stubs into
platform/tests/UNITTESTS/doubles/platform/.

Note: nvic_wrapper.h is normally implemented and used by Mbed targets
as needed. But as unit tests do not have a real target, we treat it
as a stub for the platform.

Unit tests: Move cmsis target_h stubs ...

This creates a new mbed-headers-cmsis which is always and only used
by mbed-headers-platform, so we add the former to the laters' linked
targets.

Unit tests: Move cellular target_h stubs ...

We move test-specific files from the top-level UNITTESTS directory
into individual components' UNITTESTS/doubles subdirectories.

Unit tests: Remove unused syslimits.h

Unit tests: Remove unused nsapi_ppp.h stub

Unit tests: Remove unused arm_math.h

CMake: Move ble fakes into FEATURE_BLE double dir ...

Previously ble fakes as part of UNITTESTS/fakes, this PR moves
ble fakes to FEATURE_BLE double directory to make ble stubs
to be self-contained.

CMake: fakes ble: Remove trailing whitespace

CMake: Create mbed-headers-ble library ...

Previously ble headers are part of mbed-headers-connectivity, this PR
moves ble headers into new mbed-headers-ble to make ble stubs to be
more self-contained and improves the composition of the library.

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: Move nanostack libservice stubs to the connectivity/libraries dir ...

Move the connectivity nanostack-libservice stubs into the connectivity/libraries
directory where the nanostack libservice component present as nanostack
libservice source copied from the external repo. So we can avoid duplicating
the mbed-os source tree in a central UNITTESTS folder.

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

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

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.

Merge pull request #14824 from paul-szczepanek-arm/persistence-fix ...

BLE: Manual BLE security manager db synchronisation

CMake: Move events fakes into events double dir ...

Previously events fakes as part of UNITTESTS/fakes, this PR moves
events fakes to events double directory to make events stubs
to be self-contained.

Remove trailing space

CMake: Move events stub headers to the events/tests/UNITTESTS/double dir ...

Move events stubs headers to the mbed-os/events/tests/UNITTESTS/double
directory and update double CMake to include stub headers

CMake: unit-tests: Move mbed-headers-events to the events directory ...

Move the header-only mbed-headers-events library the unit test stubs
depend on into the events component directory. This makes the events
stubs more self-contained and improves the composition of the library.

CMake: Move events stubs sources to the mbed-os/events directory ...

Move the events stub into the events 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

Merge pull request #14873 from ARMmbed/move_connectivity_netsocket_stubs ...

Move connectivity netsocket stubs