Ignore case when checking for Direct Memory OOM

[ege-st]

We have seen cases where the fault message for a Direct Memory OOM uses different casing for the phrase Direct buffer. Which meant the Direct Memory OOM Handler in the Pinot Netty code was not triggered and, so, the OOM was not cleaned up, leaving Pinot in a failed state.

This PR changes the if check to ignore case when checking the fault message.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 61.85%. Comparing base (59551e4) to head (cecc4a8).
Report is 131 commits behind head on master.

Files	Patch %	Lines
.../apache/pinot/core/transport/DirectOOMHandler.java	0.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #12657      +/-   ##
============================================
+ Coverage     61.75%   61.85%   +0.10%     
+ Complexity      207      198       -9     
============================================
  Files          2436     2452      +16     
  Lines        133233   133841     +608     
  Branches      20636    20767     +131     
============================================
+ Hits          82274    82793     +519     
- Misses        44911    44930      +19     
- Partials       6048     6118      +70     

Flag	Coverage Δ
custom-integration1	<0.01% <0.00%> (-0.01%)	⬇️
integration	<0.01% <0.00%> (-0.01%)	⬇️
integration1	?
integration2	0.00% <0.00%> (ø)
java-11	61.82% <0.00%> (+0.11%)	⬆️
java-21	34.94% <0.00%> (-26.69%)	⬇️
skip-bytebuffers-false	61.81% <0.00%> (+0.07%)	⬆️
skip-bytebuffers-true	34.94% <0.00%> (+7.21%)	⬆️
temurin	61.85% <0.00%> (+0.10%)	⬆️
unittests	61.85% <0.00%> (+0.10%)	⬆️
unittests1	46.92% <0.00%> (+0.03%)	⬆️
unittests2	27.74% <0.00%> (+<0.01%)	⬆️

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[ege-st]

The original PR did not have any unit or integration tests. Would be nice to take this chance to add a test or two, if anyone can give me a pointer on where that should go.

[soumitra-st]