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
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
In the past, when we want to modify some BE configs, we have to modify be.conf and then restart BE.
This patch provides a way to modify configs in the type of 'threshold', 'interval', 'enable flag'
when BE is running without restarting it.
You can update a single config once by BE's http API: `be_host:be_http_port/api/update_config?config_name=new_value`
