feat: debug metrics

[seemk]

• New environment variable SPLUNK_DEBUG_METRICS_ENABLED, defaults to false.
• If debug metrics are enabled, the following duration (ns) metrics will be collected from the profiler steps and reported as histograms:
  • splunk.profiler.cpu.start.duration
  • splunk.profiler.cpu.stop.duration
  • splunk.profiler.cpu.process.duration
  • splunk.profiler.heap.collect.duration
  • splunk.profiler.heap.process.duration

Additional changes:

• Removed text based profiling data collection and export as the code path was completely unused.
• As mocha runs tests in a process pool, we need a way to run tests in fresh processes due to global nature of instrumentation. For now I just added a separate testing step.

[codecov-commenter]

Codecov Report

Patch coverage: 98.07% and project coverage change: +0.50 🎉

Comparison is base (c2c2c75) 85.49% compared to head (cd5cab8) 85.99%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #700      +/-   ##
==========================================
+ Coverage   85.49%   85.99%   +0.50%     
==========================================
  Files          27       28       +1     
  Lines        1220     1264      +44     
  Branches      277      285       +8     
==========================================
+ Hits         1043     1087      +44     
  Misses        177      177              

Impacted Files	Coverage Δ
src/profiling/OTLPProfilingExporter.ts	36.06% <0.00%> (ø)
src/profiling/types.ts	100.00% <ø> (ø)
src/metrics/debug_metrics.ts	100.00% <100.00%> (ø)
src/metrics/index.ts	94.73% <100.00%> (+0.33%)	⬆️
src/profiling/index.ts	92.45% <100.00%> (+0.21%)	⬆️
src/profiling/utils.ts	90.90% <100.00%> (ø)

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