Improve ANR detector runnable

[0xnm]

What does this PR do?

This PR changes a bit ANR detection mechanism to move away from the shared (between main thread and detector thread) synchronization object to the CountDownLatch.

This should reduce the execution cost of the detector callback from the main thread by not waiting to acquire the lock if detector thread is performing long operation when ANR is registered (addError may be a long waiting call if context queue is full and blocks till ready to accept new item).

Here is the benchmark results in case if getting thread info (or reporting to RUM monitor) takes 5ms. It compares the detector callback execution from the main thread between new implementation vs previous one.

ANR threshold is set to 1s, ANR test blocks thread for 1.05s, each scenario was executed 100 times with 20 warm-up iterations before.

Scenario	Metric	Current	Original	Original / Current
No-ANR 5ms	mean	19.886 us	19.802 us	1.00x
No-ANR 5ms	p50	16.833 us	17.083 us	1.01x
No-ANR 5ms	p95	33.958 us	32.333 us	0.95x
No-ANR 5ms	p99	80.125 us	43.500 us	0.54x
No-ANR 500ms	mean	23.262 us	25.879 us	1.11x
No-ANR 500ms	p50	17.917 us	19.417 us	1.08x
No-ANR 500ms	p95	54.667 us	55.542 us	1.02x
No-ANR 500ms	p99	76.625 us	135.250 us	1.76x
ANR	mean	14.681 us	13.228 us	0.90x
ANR	p50	11.458 us	12.125 us	1.06x
ANR	p95	30.416 us	24.584 us	0.81x
ANR	p99	59.167 us	25.666 us	0.43x

Here are results if getting thread info (or reporting to RUM monitor) takes 500 ms instead.

Scenario	Metric	Current	Original	Original / Current
No-ANR 5ms	mean	13.338 us	16.664 us	1.25x
No-ANR 5ms	p50	12.542 us	12.500 us	1.00x
No-ANR 5ms	p95	26.916 us	28.208 us	1.05x
No-ANR 5ms	p99	37.917 us	31.500 us	0.83x
No-ANR 500ms	mean	51.588 us	62.442 us	1.21x
No-ANR 500ms	p50	43.542 us	25.584 us	0.59x
No-ANR 500ms	p95	126.750 us	74.250 us	0.59x
No-ANR 500ms	p99	363.750 us	560.000 us	1.54x
ANR	mean	8.787 us	457129.942 us	52021.90x
ANR	p50	6.125 us	456356.792 us	74507.23x
ANR	p95	15.917 us	465837.667 us	29266.68x
ANR	p99	17.666 us	468173.666 us	26500.32x

It can be seen, that with the original approach trying to acquire the monitor when detector has long reporting routine comes with long wait as well, which is not there for the new approach.

Other results are mixed, but given the overall time (dozens of microseconds) it is okay.

100-400 us timings in the table above are probably outliers. Detector runnable just calls countDown(), and time should be more or less in the same ballpark.

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Make sure you discussed the feature or bugfix with the maintaining team in an Issue
• Make sure each commit and the PR mention the Issue number (cf the CONTRIBUTING doc)

[codecov-commenter]

Codecov Report

❌ Patch coverage is 70.58824% with 15 lines in your changes missing coverage. Please review.
✅ Project coverage is 71.25%. Comparing base (da85551) to head (d5cc76c).
⚠️ Report is 2 commits behind head on develop.

Files with missing lines	Patch %	Lines
...og/android/rum/internal/anr/ANRDetectorRunnable.kt	70.59%	14 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3192      +/-   ##
===========================================
- Coverage    71.31%   71.25%   -0.06%     
===========================================
  Files          929      929              
  Lines        34442    34457      +15     
  Branches      5813     5813              
===========================================
- Hits         24562    24551      -11     
- Misses        8247     8263      +16     
- Partials      1633     1643      +10     

Files with missing lines	Coverage Δ
...og/android/rum/internal/anr/ANRDetectorRunnable.kt	67.61% <70.59%> (-14.54%)	⬇️

... and 41 files with indirect coverage changes

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[hamorillo]

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[hamorillo]

Nice refactor! It looks much cleaner now!