Consider custom xUnit test start/end logging

The default xUnit console logger doesn't indicate when a test starts running, only when it completes. Consider using a custom xUnit test framework to emit start/end and warn on lon-running tests, as described here:

https://andrewlock.net/tracking-down-a-hanging-xunit-test-in-ci-building-a-custom-test-framework/

This would enhance our pipeline test output, making it easier to identify tests that hang or are running long.