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.
- 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
Production code should not contain any test-specific checks. Rather
than checking `UNITTEST`, unit tests can directly set
`MBED_CONF_RTOS_PRESENT=1` to make RTOS available for testing.
Note: The cellular ATHandler test also has `MBED_CONF_RTOS_PRESENT=1`
added because `ATHandler.cpp` contains a check of this variable.
Move the header-only mbed-headers-rtos library the unit test stubs
depend on into the rtos component directory. This makes the rtos
stubs more self-contained and improves the composition of the library.
Move rtos stubs headers to the mbed-os/rtos/tests/UNITTESTS/double
directory and update CMake to create a mbed-stubs-rtos-headers
library for rtos stub headers