Debug failing HttpEventCollector_Log4j2Test

[stevejagodzinski]

Confirm that the HttpEventCollector_Log4j2Test is failing on the main branch.

The test is failing in both #207 and #208

I suspect the test failure is unrelated to any changes from those pull requests, and will fail also on the main branch.

Unfortunately, the println statements from the failing test are missing from the GitHub CI output.

This pull request aims to further debug this failing test by:
Adding a TestWatcher rule to log test name on start,
Consolidate the "Test Pass" messages,
And, flush stdout when each test completes.

You can see here (https://github.com/splunk/splunk-library-javalogging/runs/4001980946?check_suite_focus=true#step:6:1111) that the output from the failing test is not included.

I would expect to see the output from the System.out.println statements here: https://github.com/stevejagodzinski/splunk-library-javalogging/blob/feature/use-jdk8-source-features/src/test/java/HttpEventCollector_Log4j2Test.java#L269

[vmalaviya-splunk]

Thanks, @stevejagodzinski for creating the PR.
All the tests passed after merging PR#207. Reference: https://github.com/splunk/splunk-library-javalogging/actions/runs/1776788274