- Fix some logic errors in top level cmakelists related to building greentea tests
- Fix mbed_create_distro() for OBJECT libraries

CMSIS provides both GNU and legacy ARM assembly files. Instead of using
armasm and legacy asm with ARM Compiler 6, CMakeLists is modified to
use the GNU format with both GCC_ARM and ARM C6.

- 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.

mbed-os consists of mbed-core and mbed-rtos
mbed-baremetal consists of mbed-core

The main change is for mbed-core. Changing from object library to be interface. This way it allows us to do the above to have 2 main targets for users to use.

This should be backward compatible change as mbed-os target we used contains the same files/options as previously set.

Add or remove and directories containing source files, header files, and macro definitions that implement RTOS support.
This includes:
- cmsis/CMSIS_5/CMSIS/RTOS2/
- cmsis/device/rtos/
- rtos/source/ConditionVariable.cpp
- rtos/source/Thread.cpp

* mbed-os renamed mbed-core
* mbed-os-<COMPONENT> renamed mbed-<COMPONENT>