[fix][test] Fix flaky test NonPersistentTopicTest.testMsgDropStat, 3rd attempt

[lhotari]

Fixes #20386

Motivation

• the previous attempts [fix][test] Fix flaky test NonPersistentTopicTest.testMsgDropStat #20387 and [fix][test] Fix flaky test NonPersistentTopicTest.testMsgDropStat, follow up #20401 to fix the flakiness weren't effective alone

Modifications

• add .ignoreExceptions() to Awaitility call
  • underlying issue was IndexOutOfBoundsException which doesn't get retried by Awaitility unless .ignoreExceptions() has been called. The root cause was hidden by TestNG retries. There's another PR to improve this by adding some logging, [improve][ci] Improve TestNG test execution to debug flaky test failures #20425
  • docs for ignoreExceptions(): https://github.com/awaitility/awaitility/wiki/Usage#ignoring-exceptions
• general test logic improvements
  • use unique topic name
  • use Closeable to close producer and consumers
  • assert that the latch was triggered

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

[codecov-commenter]

Codecov Report

Merging #20429 (7334b4a) into master (b5ef09e) will decrease coverage by 0.05%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master   #20429      +/-   ##
============================================
- Coverage     72.92%   72.87%   -0.05%     
+ Complexity    31897    31865      -32     
============================================
  Files          1865     1865              
  Lines        138439   138439              
  Branches      15192    15192              
============================================
- Hits         100953   100888      -65     
- Misses        29474    29537      +63     
- Partials       8012     8014       +2     

Flag	Coverage Δ
inttests	24.16% <ø> (+0.01%)	⬆️
systests	24.91% <ø> (+0.02%)	⬆️
unittests	72.16% <ø> (-0.06%)	⬇️

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see 56 files with indirect coverage changes