optimizations of Tx Hash handling

[pompon0]

• Merged Tx.Hash and Tx.Key into one method to avoid confusion
• Added hashedTx wrapper type which keeps precomputed TxHash

[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	Apr 28, 2026, 1:52 PM

[codecov]

Codecov Report

❌ Patch coverage is 75.70093% with 52 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.23%. Comparing base (d67dd88) to head (cbcd939).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
sei-tendermint/internal/mempool/mempool.go	56.25%	19 Missing and 2 partials ⚠️
sei-tendermint/internal/state/execution.go	20.00%	8 Missing ⚠️
app/ante/evm_checktx.go	0.00%	4 Missing ⚠️
giga/deps/xevm/keeper/keeper.go	75.00%	3 Missing and 1 partial ⚠️
x/evm/keeper/keeper.go	75.00%	3 Missing and 1 partial ⚠️
sei-tendermint/internal/rpc/core/mempool.go	57.14%	3 Missing ⚠️
sei-tendermint/types/mempool.go	83.33%	3 Missing ⚠️
x/evm/ante/sig.go	50.00%	2 Missing ⚠️
sei-cosmos/server/rosetta/client_online.go	0.00%	1 Missing ⚠️
sei-tendermint/internal/consensus/state.go	66.66%	1 Missing ⚠️
... and 1 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3314      +/-   ##
==========================================
+ Coverage   59.19%   59.23%   +0.03%     
==========================================
  Files        2097     2097              
  Lines      172482   172493      +11     
==========================================
+ Hits       102106   102170      +64     
+ Misses      61532    61490      -42     
+ Partials     8844     8833      -11     

Flag	Coverage Δ
sei-chain-pr	68.31% <75.70%> (?)
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-tendermint/crypto/crypto.go	100.00% <100.00%> (ø)
sei-tendermint/crypto/merkle/hash.go	100.00% <100.00%> (ø)
sei-tendermint/internal/mempool/cache.go	96.93% <100.00%> (ø)
sei-tendermint/internal/mempool/reactor/reactor.go	84.09% <100.00%> (ø)
sei-tendermint/internal/mempool/tx.go	78.00% <100.00%> (+0.11%)	⬆️
sei-tendermint/internal/rpc/core/tx.go	64.78% <100.00%> (ø)
sei-tendermint/internal/state/indexer/tx/kv/kv.go	66.21% <100.00%> (+0.11%)	⬆️
sei-tendermint/rpc/coretypes/requests.go	71.05% <ø> (ø)
sei-tendermint/types/block.go	86.19% <100.00%> (ø)
sei-tendermint/types/evidence.go	75.65% <100.00%> (+0.10%)	⬆️
... and 13 more

... and 6 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.

[wen-coding]

nit: I like what you are doing in this PR. But I'm a bit worried that we need to change so many tests. Would it make our lives easier to have a constructor
NewWrappedTx(tx types.Tx, opts...) instead so we don't give the tests a chance to know about newHashedTx?

[pompon0]

Although I do agree that strengthening WrappedTx type and making tests internals agnostic would benefit the correctness, I decided to scope down this pr to just hash field protection to limit the diff size. Afaict all the test changes are mechanical and personally I feel comfortable with making them.