Performance improvements for file logging

[mathewc]

Making some performance improvements to file logging based on a recent CRI investigation. In that investigation, we were seeing thread exhaustion in the host process with many threads blocked on file IO. When the issue occurred, the app had FileLoggingMode enabled (see doc for fileLoggingMode) because they had the portal open on the app. This causes the log stream to also go to files. At the time the app was under high load, so there was a lot of file logging happening. Compounding things was the fact that the customer was also logging errors, triggering our "force flush on error" logic.

Pull request checklist

• My changes do not require documentation changes
  • Otherwise: Documentation issue linked to PR
• My changes should not be added to the release notes for the next release
  • Otherwise: I've added my notes to release_notes.md
• My changes do not need to be backported to a previous version
  • Otherwise: Backport tracked by issue/PR #issue_or_pr
• My changes do not require diagnostic events changes
  • Otherwise: I have added/updated all related diagnostic events and their documentation (Documentation issue linked to PR)
• I have added all required tests (Unit tests, E2E tests)

[fabiocav]

Approved the changes, but some of the tests seem to be failing here, likely due to the timing difference introducing races.