[unit test] use nicemock to remove the excessive gmock warnings.

[georgeliao]

Remove the excessive gmock warnings from unit tests.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 88.82%. Comparing base (71d73f3) to head (671964d).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #3517 +/- ## ========================================== - Coverage 88.82% 88.82% -0.01% ========================================== Files 254 254 Lines 14115 14115 ========================================== - Hits 12538 12537 -1 - Misses 1577 1578 +1 ```

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