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
from/to_base64 may return incorrect value when the value is null #4130
remove the duplicated base64 code
fix the base64 encoded string length is wrong， and this will cause the memory error
