Unit tests: Create mbed-headers-kvstore ...

Create a CMake target mbed-headers-kvstore to separate KVStore headers
from the generic mbed-headers-storage. Update tests to use it.

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.

CMake: rename greentea test macro

CMake: Add support for KVstore Greentea tests ...

The KVstore Greentea tests can now be built with CMake

KVStore general_tests_phase_1/2: flash simulation no longer required

Relocate kvstore Greentea tests into each store type's path

Relocate kvstore unit tests into each store type's path

Update UNITTEST for kvstore

Update include paths

Bring in TDBStore UNITTESTS improvements from PR #13731 ...

Co-authored-by: Seppo Takalo <seppo.takalo@arm.com>

general_tests_phase_2: SecureStore's underlying TDBStore must be large enough ...

The test case set_add_data_set_key_value_five_Kbytes stores
5KB of value, and to allow for overheads, we allocate at least
8KB per area of TDBStore (so 16KB for two areas of a whole
TDBStore).

kvstore general_tests_phase_1/2 tests: Skip TDBStore if FlashIAP sector size is non-uniform ...

By default TDBStore requires blocks to have the same size.

Merge pull request #13484 from jeromecoutant/PR_KVSTORE_TESTS ...

KVSTORE tests: move directories

Move mbed-trace into platform

KVSTORE tests: move directories to make shorter test name ...

This allows compilation in Windows environment with name length constraint

move greentea and UNITTESTS closure to library