Fix MBED_ASSERT for UTs
Fix MBED_ASSERT for UTs

For UTs mbed_assert_internal should not be declared as MBED_NORETURN
as UT stub for mbed_assert_internal only prints out the assert trace
and returns back to original code.

kjbracey-arm/mbed,mbedmicro/mbed,andcor02/mbed-os,andcor02/mbed-os,mbedmicro/mbed,kjbracey-arm/mbed,mbedmicro/mbed,andcor02/mbed-os,andcor02/mbed-os,kjbracey-arm/mbed,mbedmicro/mbed,andcor02/mbed-os,kjbracey-arm/mbed,andcor02/mbed-os,mbedmicro/mbed