bank: sdk.Int object pool to reduce allocations in balance reads

[codchen]

Summary

• Introduces SdkIntPool (backed by sync.Pool) on BaseViewKeeper, stored as intPool *SdkIntPool
• sdk.Int.Unmarshal already reuses the existing *big.Int when non-nil, so a pooled entry skips the big.Int allocation on subsequent unmarshal calls
• All direct sdk.Int storage reads in the bank keeper (GetWeiBalance, GetSupply, GetPaginatedTotalSupply, IterateAllWeiBalances, IterateTotalSupply) now borrow from the pool instead of allocating fresh per call
• Iterator paths borrow a single pool entry for the entire iteration — one big.Int allocation total instead of 2N; callbacks that need to retain the value past the callback must copy via i.BigInt() (documented in the IterateAllWeiBalances comment)
• genesis.go's IterateAllWeiBalances callback, which stores values into a slice, is updated to call sdk.NewIntFromBigInt(i.BigInt()) for an explicit deep copy

Test plan

• Existing sei-cosmos/x/bank/keeper unit tests pass (go test ./sei-cosmos/x/bank/keeper/...)
• Verify genesis export round-trip (wei balances are not corrupted)
• Run invariant checks to confirm IterateAllWeiBalances still produces correct totals

🤖 Generated with Claude Code

[github-actions]

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Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	May 4, 2026, 4:10 AM

[codecov]

Codecov Report

❌ Patch coverage is 77.77778% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.17%. Comparing base (6620fb6) to head (2ec955d).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
sei-cosmos/x/bank/keeper/keeper.go	69.23%	1 Missing and 3 partials ⚠️
sei-cosmos/x/bank/keeper/view.go	63.63%	1 Missing and 3 partials ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3373   +/-   ##
=======================================
  Coverage   59.17%   59.17%           
=======================================
  Files        2097     2098    +1     
  Lines      172641   172659   +18     
=======================================
+ Hits       102163   102179   +16     
- Misses      61615    61617    +2     
  Partials     8863     8863           

Flag	Coverage Δ
sei-chain-pr	78.19% <77.77%> (?)
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-cosmos/x/bank/keeper/genesis.go	76.59% <100.00%> (ø)
sei-cosmos/x/bank/keeper/pool.go	100.00% <100.00%> (ø)
sei-cosmos/x/bank/keeper/keeper.go	79.93% <69.23%> (-0.19%)	⬇️
sei-cosmos/x/bank/keeper/view.go	85.71% <63.63%> (-0.26%)	⬇️

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