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
Also fix BE ut:
1. fix scheme_change_test memory leak
2. fix mem_pool_test
Do not using DEFAULT_PADDING_SIZE = 0x10 in mem_pool when running ut.
3. remove plugin_test
