Build the CFE UT stub library separately from the test cases.
This moves the stub files into a separate ut-stubs directory,
and the library is now called "ut_cfe_core_stubs"

Note: Minor cleanup also done as part of moving.  Two stub
files were in the source tree but not being built or used
by any framework test config.  These were:
  ut_arinc653_stubs.c
  ut_configdata_stubs.c

These are now removed.  Also cleaned up some old macros/ifdefs
that were never enabled or used in the current tests.

Removed conflicting files, not needed after #417 changes.

Fix #415, #429
Reviewed and approved at 2019-12-18 CCB