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
Some invalid config value may cause BE work in an unexpected behavior,
this patch aim to support config validating when BE bootstrap and update BE's config by API
to reject invalid value.
This is a work to accomplish PR #4423
