[test] Add Optional Factor to Avoid Races and Skip Committing Coverage

This makes 2 updates to the regression tests:

1. Add a TIME_FACTOR environment variable that can be increased to avoid races and timeouts (doubles by default in CI now)
2. Remove the coverage metrics from source control - we can look back at the CI runs, but I foresee this becoming a pain point for rebase conflicts that will cause PRs to unnecessarily require re-approval