perf(azure-monitor-exporter): Azure monitor exporter log transformer optimizations

[gouslu]

• Reuse buffer across log records
• Schema pre-parsing to avoid parsing for each transformation
• Use enum matching instead of string comparisons for log record fields
• Use Cow for HashMap lookups and eq_ignore_ascii_case to avoid temporary strings
• Remove "disable_schema_mapping", not needed for customers

[codecov]

Codecov Report

❌ Patch coverage is 98.68421% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.08%. Comparing base (f913bbf) to head (2fbc0c4).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1731      +/-   ##
==========================================
+ Coverage   84.06%   84.08%   +0.02%     
==========================================
  Files         469      470       +1     
  Lines      136284   136558     +274     
==========================================
+ Hits       114561   114828     +267     
- Misses      21189    21196       +7     
  Partials      534      534              

Components	Coverage Δ
otap-dataflow	85.37% <98.68%> (+0.03%)	⬆️
query_abstraction	80.61% <ø> (ø)
query_engine	90.39% <ø> (ø)
syslog_cef_receivers	∅ <ø> (∅)
otel-arrow-go	53.50% <ø> (ø)

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[drewrelmas]

You mention perf improvements - do you have benchmarks of before and after? I wonder if we should add these experimental components into benchmarks like the rest of primary components.

[drewrelmas]

Not a blocker, but depending on how #1725 turns out, maybe we want to support aliases for the OpenTelemetry log data model spec naming convention. You're already partially flexible thanks to the case insensitivity.

[gouslu]

I didn't bench it particularly, but I saw an about 3%-5% throughput increase in my local tests!

[lalitb]

Remove "disable_schema_mapping", not needed for customers

Nit - This is still there in readme and yaml.

[gouslu]

addressed the comments, ready to merge.