Add benchmark overview doc

[cijothomas]

This docs is an attempt at the schema for our Phase 2 performance summary, when phase 2 is completed. It defines the key scenarios (Idle, 100k Load, Saturation) and the comparative analysis with OTLP/Collector. I've put TBD for actual numbers, as this is just attempting to finalize what we want to have in an easy to consume format. Actual numbers will be filled in later. This can also be used to see if there are gaps in the perf test suites that we want to add.

The existing pages like https://open-telemetry.github.io/otel-arrow/benchmarks/nightly/backpressure/ are still retained. This doc will have distilled information from them.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.40%. Comparing base (c738bf8) to head (3357270).
⚠️ Report is 9 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1528      +/-   ##
==========================================
- Coverage   83.45%   83.40%   -0.05%     
==========================================
  Files         426      426              
  Lines      118369   118369              
==========================================
- Hits        98779    98724      -55     
- Misses      19056    19111      +55     
  Partials      534      534              

Components	Coverage Δ
otap-dataflow	84.58% <ø> (-0.09%)	⬇️
query_abstraction	80.61% <ø> (ø)
query_engine	90.25% <ø> (ø)
syslog_cef_receivers	∅ <ø> (∅)
otel-arrow-go	53.50% <ø> (ø)

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[lquerel]

I really like this document.

I think we should also include the OTLP to OTLP scenario in the different sections since it will be one of the most common scenarios, at least in the beginning.

I also think we should add the wait_for_result mode in the otel-arrow section because it provides a true end to end unified ack/nack mechanism, which I believe is not fully supported by the Go collector.