Extend coredump_backend tests:
* fix COREDUMP_CMD_VERIFY_STORED_DUMP test was not executed.
* add tests for these coredump commands:
- COREDUMP_QUERY_GET_STORED_DUMP_SIZE,
- COREDUMP_CMD_INVALIDATE_STORED_DUMP,
- COREDUMP_CMD_ERASE_STORED_DUMP,
- COREDUMP_CMD_CLEAR_ERROR.
* extend the out-of-the-treee example 'empty' backend to
execute the new tests.
* fix the test's cmake project name.
Signed-off-by: Dmitrii Golovanov <dmitrii.golovanov@intel.com>
