Create a standard way to check events being fired in Unittest

[ChenyuLInx]

In dbt-core, we now use an event manager to handle logs. In unit tests, we want to check whether under certain conditions, dbt-core will emit certain type of logs. We have been doing this a lot in functional tests by using the run_and_capture function. In unittest, we should mock the event manager so we can check what fire_event has been called with.
AC:

• we have a standard way of checking events in unit test.
• a unit test using the new way to check events being fired.

[ChenyuLInx]

mock fire_event/ event_manager(depending on which way it is easier to mock).

[ChenyuLInx]

@ChenyuLInx link one test that we want to modify

[ChenyuLInx]

https://github.com/dbt-labs/dbt-core/pull/10009/files#r1575498113 Something related to this ticket. We should modify this test when proper mocking for logger is available.