ext: hal: cmsis: Add HAS_CMSIS_CORE configuration.

The existing implementation used HAS_CMSIS configuration to specify
that CMSIS-Core(M) is used; when, in fact, there are other CMSIS
variants available such as CMSIS-Core(A) and CMSIS-DSP available.

This commit replaces the existing HAS_CMSIS configuration with
HAS_CMSIS_CORE to clarify that CMSIS-Core is used. It also introduces
the CMSIS-Core variant configuration, HAS_CMSIS_CORE_M, that is
automatically selected when HAS_CMSIS_CORE is enabled.

For more details, see issue #19717.

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>