Check the bad block manager when receiving a new block from the network

[daniellehrner]

PR description

When we get a fcu request and need to sync missing blocks from our peers, we currently are not checking if any of those blocks is already in the bad block manager. This leads to an endless loop where we try to import an invalid block every few milliseconds.

This PR adds this check and marks all following blocks on this specific forks as invalid as well. Like this we can respond with INVALID when the next fcu request is received and correctly signal to the CL that we consider this fork invalid.

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• Checked out our contribution guidelines?
• Considered documentation and added the doc-change-required label to this PR if updates are required.
• Considered the changelog and included an update if required.
• For database changes (e.g. KeyValueSegmentIdentifier) considered compatibility and performed forwards and backwards compatibility tests

Locally, you can run these tests to catch failures early:

• spotless: ./gradlew spotlessApply
• unit tests: ./gradlew build
• acceptance tests: ./gradlew acceptanceTest
• integration tests: ./gradlew integrationTest
• reference tests: ./gradlew ethereum:referenceTests:referenceTests
• hive tests: Engine or other RPCs modified?

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Adds safeguards to avoid repeatedly attempting to import blocks already marked as bad, preventing sync loops and enabling correct INVALID signaling for poisoned forks.

Changes:

• Short-circuit new block and new block hash handling when the block hash is already in BadBlockManager.
• Add a defensive short-circuit at the start of importOrSavePendingBlock for known-bad blocks.
• Add unit tests around block propagation skipping, plus an integration test covering engine_forkchoiceUpdated behavior with bad ancestors.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 6 comments.

File	Description
ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/sync/BlockPropagationManager.java	Adds known-bad-block checks in network handlers and import path to avoid reprocessing invalid blocks.
ethereum/eth/src/test/java/org/hyperledger/besu/ethereum/eth/sync/AbstractBlockPropagationManagerTest.java	Adds tests asserting known-bad blocks are skipped before entering the import/request pipeline.
ethereum/api/src/test/java/org/hyperledger/besu/ethereum/api/jsonrpc/internal/methods/engine/EngineForkchoiceUpdatedBadAncestorIntegrationTest.java	Adds end-to-end test verifying bad-ancestor propagation yields INVALID with correct latestValidHash.