Fix flaky test: TestParquetFilePruning

[jewei1997]

Describe your changes and provide context

TestParquetFilePruning was flaky because it relied on a background pruning goroutine that fires immediately on store open. The test queried data without synchronizing with the concurrent pruning, creating a race between file deletion and DuckDB queries that failed frequently on slower hardware.

Fix:

• Disable background pruning in the test (PruneIntervalSeconds = 0) and trigger
  PruneOldFiles synchronously instead
• Export PruneOldFiles on parquet.Store (renamed from pruneOldFiles) to enable this
• Add assertions that files were actually removed from disk (before vs after
  counts), making the test more thorough
• Replace common.Big1.SetUint64(block) with new(big.Int).SetUint64(block) to avoid
  mutating a shared global

Testing performed to validate your change

go test ./sei-db/ledger_db/receipt/ -run TestParquetFilePruning -race -count=5
  -timeout 120s
go test ./sei-db/ledger_db/parquet/ -count=1 -timeout 120s
go test ./sei-db/ledger_db/receipt/ -count=1 -timeout 180s

[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	Mar 11, 2026, 4:43 PM

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 58.33%. Comparing base (30f8b0a) to head (a2fde15).

Files with missing lines	Patch %	Lines
sei-db/ledger_db/parquet/store.go	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3053      +/-   ##
==========================================
- Coverage   58.36%   58.33%   -0.03%     
==========================================
  Files        2079     2079              
  Lines      171899   171883      -16     
==========================================
- Hits       100321   100265      -56     
- Misses      62637    62672      +35     
- Partials     8941     8946       +5     

Flag	Coverage Δ
sei-chain-pr	73.95% <50.00%> (?)
sei-db	70.41% <ø> (ø)

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

Files with missing lines	Coverage Δ
sei-db/ledger_db/parquet/store.go	69.36% <50.00%> (-0.31%)	⬇️

... and 26 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.