add flag to overwrite base fee to 0 during benchmark

[codchen]

Describe your changes and provide context

Base fee is the amount of fees that get burnt for each transaction. We may or may not set it to a non-zero value depending on tokeneconomics. For benchmarking purpose, a zero base fee will allow us gauge a better best-case scenario

Testing performed to validate your change

BENCHMARK_CONFIG="scripts/scenarios/evm_fast.json" ZERO_BASE_FEE=true GIGA_EXECUTOR=true GIGA_OCC=true scripts/benchmark.sh -> 26k
GIGA_EXECUTOR=true GIGA_OCC=true scripts/benchmark.sh -> 20k

[github-actions]

The latest Buf updates on your PR. Results from workflow Buf / buf (pull_request).

Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Feb 13, 2026, 3:55 AM

[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 57.14%. Comparing base (9ccd5ca) to head (b99d758).

Files with missing lines	Patch %	Lines
app/app.go	0.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2869      +/-   ##
==========================================
- Coverage   57.16%   57.14%   -0.02%     
==========================================
  Files        2091     2091              
  Lines      171145   171150       +5     
==========================================
- Hits        97827    97810      -17     
- Misses      64609    64624      +15     
- Partials     8709     8716       +7     

Flag	Coverage Δ
sei-chain	52.60% <75.00%> (-0.02%)	⬇️
sei-cosmos	48.14% <ø> (ø)
sei-db	68.72% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
app/benchmark/benchmark.go	63.63% <100.00%> (+3.63%)	⬆️
app/app.go	72.69% <0.00%> (-0.12%)	⬇️

... and 21 files with indirect coverage changes

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