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

Move the drivers stub library into the drivers component directory.
so we can avoid duplicating the mbed-os source tree in a central
UNITTESTS folder.

CMake: unit-tests: Make drivers UNITTESTS only depend on headers it uses ...

Previously the drivers unit tests depended on `mbed-headers`, which
is a collection of all available headers in mbed-os. To make it easier
to separate the library, only depend on the headers we're using.

CMake: unit-tests: Pwmout & Watchdog: Remove trailing whitespace

Fix hanging with multiple I2C buses ...

Make the _mutex non-static and remove _owner and acquire()

When two or more I2C buses are used then static__mutex and _owner are
shared between all I2C class instances in the program. That
wastes time to reconfigure periphery on every transfer.

Make _mutex non-static. Remove _owner and acquire() method
because in non-static case they have no practical meaning.

CMake: Only build unit tests if Mbed OS is the current project ...

Typically when adding a unit test directory to a CMake project a check
will be used to ensure the subdirectory is added only if the following
are true:

* The BUILD_TESTING option is set to ON.
* The current CMake project is the top-level project.

The reason being, if a downstream project includes our project they
generally don't want to build our unit tests.

In mbed-os, we do correctly specify the above condition before adding
the central UNITTEST subdirectory, which fetches googletest and adds the
"stub" libraries the unit tests depend on. However, we only check if
CMAKE_CROSSCOMPILING is OFF (or undefined) before actually adding the
unit tests. This mismatched logic would lead to unexpected build
failures in various scenarios. One likely case could be: a downstream
project including mbed-os happens to set CMAKE_CROSSCOMPILING to
OFF/undefined for any reason (possibly to build its own unit tests).
mbed-os would go ahead and attempt to build its tests without fetching
googletest or adding the required stub targets.

To fix the issue replace the check for CMAKE_CROSSCOMPILING in the unit
tests with the same BUILD_TESTING idiom we use for adding the central
UNITTESTS subdirectory.

Merge pull request #14675 from 0xc0170/fix_i2c_start ...

i2c: `start()` should aquire the bus

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

Merge pull request #14662 from AGlass0fMilk/can-message-comparison-operators ...

Add CANMessage deep comparison operators

Merge pull request #14678 from ghseb/uartserial-shadowing-2 ...

Serial: remove shadowing member variables

Merge pull request #14426 from ARMmbed/feature_unittest_refactor ...

CMake: Refactor UNITTESTS CMake

Remove shadowing member variables ...

- The variables shadow SerialBase::_tx_enabled and SerialBase::_rx_enabled
- Update interrupts when input/output is enabled to avoid infinite congestion
- Update comments

Add CANMessage deep comparison operators

i2c: `start()` should aquire the bus ...

From the history it looks like aquire was not added explicitely to start. I do not see
why as it's the condition that must be sent when communication is initiated.

write/read/transfer invoke `aquire()`

Merge pull request #14336 from AGlass0fMilk/polymorphic-can ...

Implement polymorphism for CAN driver

CMake: Refactor drivers unittest cmake

CMake: Add add_subdirectory of unittests ...

- add every libraries unittest directory into respective CMake
  which allows to include unittest source into build based on
  MBED_BUILD_UNITTESTS flag

Merge pull request #14588 from Patater/mbed-libs-for-m55 ...

Add v8.1-M architecture awareness

Replace NonCopyable in CAN inheritance. ...

This commit moves the deletion of copy constructor and copy assignment operators to the `mbed::interface::can` class, where both `mbed::CAN` and `mbed::interface::CAN` inherit enum types from. This allows `NonCopyable` to be removed from the inheritance list.

Fix astyle CI failures

Make interface::CAN buildable on targets without DEVICE_CAN ...

This commit adds provisions to enable using interface::CAN on targets that don't have DEVICE_CAN set to 1 (ie: they don't normally have a CAN peripheral).

Enable inheritance of CAN enum types ...

This commit changes the `interface::can` namespace to a `struct`. This allows the enum types to be inherited and prevents breaking old code relying on referencing eg: `CAN::RxIrq`.

When enabled, the polymorphic CAN interface class inherits from this `interface::can` struct. If not enabled, the `mbed::CAN` class inherits from `interface::can` directly.

Co-authored-by: Vincent Coubard <vincent.coubard@arm.com>

Implement polymorphism for CAN

Merge pull request #14589 from plan-do-break-fix/Typo-corrections ...

fix(docs): corrects various typos in project documentation

fix(docs): corrects various typos in project documentation

Add v8.1-M architecture awareness ...

Add v8.1-M architecture awareness to Mbed CRC, HAL, and Mbed Atomic.

Fixes #14433

Fix DeviceKey documentation regarding RoT ...

Since the commit

    0e7a53c DeviceKey Root of Trust generation refactored.

the Root of Trust is not automatically generated anymore.

Merge pull request #14457 from ARMmbed/uart-stdio-alias ...

Update UART pin names & add MBED_CONF_TARGET_STDIO_UART overrides

Merge pull request #14437 from ARMmbed/qspi-fix ...

Remove ownership/acquire in QSPI/OSPI driver

Replace USBTX/RX

Replace USBTX/RX everywhere else