#13195 left some unresolved issues. One of them is that some BE unit tests fail.
This PR fixes this issue. Now, we can run the command ./run-be-ut.sh --run successfully on macOS.
1. solved the previous delayed unit test file size is too large (1.7G+) and the unit test link time is too long problem problems
2. Unify all unit tests into one file to significantly reduce unit test execution time to less than 3 mins
3. temporarily disable stream_load_test.cpp, metrics_action_test.cpp, load_channel_mgr_test.cpp because it will re-implement part of the code and affect other tests
