fix(benchmarks): Bump max_decoding_message_size to 32MiB to fix batch processor benchmarks

[JakeDern]

Change Summary

Batch processor benchmarks had 100% signal drop rate due to being over the decompression limit on the backend engine. Bumping the limit fixes the issue for both continuous and nightly.

What issue does this PR close?

• Closes OTLP->BATCH-OTLP scenario is showing 100% dropped for all three signaly types in nightly and continuous benches #2729

How are these changes tested?

Ran all scenarios locally and observed the dropped rate being 0 (or less):

Are there any user-facing changes?

No

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.87%. Comparing base (dd34485) to head (9c8995c).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2730      +/-   ##
==========================================
- Coverage   87.87%   87.87%   -0.01%     
==========================================
  Files         638      638              
  Lines      244608   244608              
==========================================
- Hits       214950   214944       -6     
- Misses      29134    29140       +6     
  Partials      524      524              

Components	Coverage Δ
otap-dataflow	89.90% <ø> (-0.01%)	⬇️
query_abstraction	80.61% <ø> (ø)
query_engine	90.74% <ø> (ø)
otel-arrow-go	51.92% <ø> (ø)
quiver	92.27% <ø> (ø)

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