chore: use fixed size thread pool for rxjava invocations

[codecov[bot]]

Codecov Report

Merging #415 (b91a339) into main (459c0ec) will decrease coverage by 0.17%. The diff coverage is 20.00%.

@@             Coverage Diff              @@
##               main     #415      +/-   ##
============================================
- Coverage     79.87%   79.70%   -0.17%     
  Complexity     1423     1423              
============================================
  Files           128      128              
  Lines          5585     5598      +13     
  Branches        511      511              
============================================
+ Hits           4461     4462       +1     
- Misses          890      902      +12     
  Partials        234      234              

Flag	Coverage Δ
unit	79.70% <20.00%> (-0.17%)	:arrow_down:

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Files Changed	Coverage Δ
...cher/enrichment/clients/DefaultClientRegistry.java	0.00% <0.00%> (ø)
.../accessor/entities/TraceEntityAccessorBuilder.java	0.00% <0.00%> (ø)
.../accessor/entities/DefaultTraceEntityAccessor.java	96.80% <100.00%> (+0.03%)	:arrow_up:

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Unit Test Results

  78 files  ±0    78 suites  ±0   1m 44s :stopwatch: -10s 418 tests ±0  418 :heavy_check_mark: ±0  0 :zzz: ±0  0 :x: ±0 

Results for commit b91a3392. ± Comparison against base commit 459c0ec2.

[saxenakshitiz]

This change is not required.

We added a different change - https://github.com/hypertrace/hypertrace-ingester/pull/416