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.
It was removed in 6.0 (see reference below), and it was reintroduced when we updated
cmsis from the upstream. We missed to remove the commit adding the file in the cmsis
importer. This fixes it and the file should not be introduced again.
Fixes#13823
Already removed in 6.0: https://github.com/ARMmbed/mbed-os/pull/12055