fix(mempool)!: Remove VM keeper end blocker notification, use PrepareCheckStater instead

[mattac21]

Description

Removes the ability to notify the mempool of new blocks within the vm keepers end blocker. This is strictly incorrect now since it will trigger a reset of the mempool on stale state. This behavior is replicated by using the PrepareCheckStater hook that is called just after a block is committed and the check state is updated.

Closes: STACK-2688

---

Author Checklist

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I have...

• tackled an existing issue or discussed with a team member
• left instructions on how to review the changes
• targeted the main branch

[greptile-apps]

Greptile Summary

This PR removes the incorrect EndBlocker-based mempool notification (which ran on stale pre-commit state) and replaces it with a PrepareCheckStater hook that fires after a block is committed and check state is refreshed. The evmMempool field and SetEvmMempool/NotifiedMempool interface surface are fully cleaned up. All three issues flagged in previous review rounds — the P0 compile error, the stale doc comment, and the dead struct field — are resolved in this changeset.

Confidence Score: 5/5

Safe to merge — all previously flagged issues are resolved and no new P0/P1 issues found

The three issues from previous review rounds (P0 compile error, stale doc comment, dead struct field) are all cleanly fixed. The new PrepareCheckStater hook fires at the correct lifecycle point, the NotifyNewBlock() refactor preserves both the blockchain notification and cosmos pool recheck in both paths, and all interface/mock/import cleanup is consistent.

No files require special attention

Important Files Changed

Filename	Overview
evmd/mempool.go	Adds SetPrepareCheckStater hook that calls mempool.NotifyNewBlock() only when no event bus is configured; correctly replaces EndBlocker notification
mempool/mempool.go	Extracts NotifyNewBlock() as a public method (blockchain notify + cosmos recheck trigger); removes vmKeeper.SetEvmMempool call; event-bus goroutine now delegates to the new method
mempool/interface.go	Removes NotifiedMempool interface and SetEvmMempool from VMKeeperI; GetBlockchain() still exported on *Mempool but no longer part of any interface
x/vm/keeper/abci.go	Removes the stale-state mempool notification from EndBlock; EndBlock now only calls CollectTxBloom
x/vm/keeper/keeper.go	Removes evmMempool field and SetEvmMempool method from the Keeper struct; import of evmmempool package also cleaned up
mempool/mocks/VMKeeperI.go	Mock updated to remove SetEvmMempool entry and the now-unused mempool import
CHANGELOG.md	Adds API-BREAKING entry for the EndBlocker to PrepareCheckStater migration under a new section

Sequence Diagram

sequenceDiagram
    participant CometBFT
    participant BaseApp
    participant EVMKeeper
    participant Mempool

    note over CometBFT,Mempool: Old flow (removed)
    CometBFT->>BaseApp: FinalizeBlock
    BaseApp->>EVMKeeper: EndBlock
    EVMKeeper-->>Mempool: NotifyNewBlock (stale state)

    note over CometBFT,Mempool: New flow (this PR)
    CometBFT->>BaseApp: FinalizeBlock + Commit
    BaseApp->>BaseApp: Update check state
    BaseApp->>Mempool: PrepareCheckStater hook
    alt no event bus configured
        Mempool->>Mempool: NotifyNewBlock()
        Mempool->>Mempool: recheckCosmosPool.TriggerRecheck()
    else event bus configured
        CometBFT-->>Mempool: EventBus subscription fires
        Mempool->>Mempool: NotifyNewBlock()
        Mempool->>Mempool: recheckCosmosPool.TriggerRecheck()
    end

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_{Reviews (2): Last reviewed commit: "Merge branch 'main' into ma/remove-mempo..." | Re-trigger Greptile}

[mattac21]

@greptile re review pls

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 66.20%. Comparing base (4b69c4e) to head (eee1af2).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1146      +/-   ##
==========================================
+ Coverage   65.27%   66.20%   +0.93%     
==========================================
  Files         336      336              
  Lines       23903    23844      -59     
==========================================
+ Hits        15602    15787     +185     
+ Misses       6937     6885      -52     
+ Partials     1364     1172     -192     

Files with missing lines	Coverage Δ
mempool/mempool.go	81.29% <100.00%> (+22.53%)	⬆️
x/vm/keeper/abci.go	90.47% <ø> (-0.83%)	⬇️
x/vm/keeper/keeper.go	89.52% <ø> (-0.11%)	⬇️

... and 14 files with indirect coverage changes

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[linear]

STACK-2688 Remove `EndBlocker` mempool notifications`