feat: support CopyTrie() for reconstructed tries

[RodrigoVillar]

Why this should be merged

Previously, trying to copy a reconstructed account trie returned nil as reconstructed revisions (i.e. the pointer backing reconstructed account tries) are not safe to share. However, methods such as eth_accessList and eth_estimateGas call CopyTrie() - in the case that the trie is a reconstructed account trie, this would eventually result in these operations trying to read against a nil-pointer, resulting in failed queries.

This PR fixes this by enabling CopyTrie() to deep copy a reconstructed account trie if one is passed in.

How this works

This PR adds a Copy() method to the reconstructed account trie type which returns a deep copy. This method utilizes the Clone() method which was added as part of Firewood v0.5.0.

How this was tested

CI + added two UTs:

• TestReconstructedCopyTrie()
• TestFirewoodCopyTrie()

Need to be documented in RELEASES.md?

No

[Copilot]

Pull request overview

This PR fixes failures in RPC paths (e.g., eth_accessList, eth_estimateGas) when they call CopyTrie() on reconstructed account tries by adding support for deep-copying reconstructed tries rather than returning nil.

Changes:

• Added (*reconstructedAccountTrie).Copy() that clones the underlying ffi.Reconstructed handle and rebinds the base trie reader to the clone.
• Updated reconstructedStateAccessor.CopyTrie() to return a copied reconstructed trie (and log on copy errors) instead of always returning nil.
• Added unit test TestReconstructedCopyTrie() to validate the copied trie is usable and independent.

Reviewed changes

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

File	Description
graft/evm/firewood/reconstructed_trie.go	Adds Copy() to deep-copy reconstructed tries by cloning the ffi.Reconstructed handle and rebinding the reader.
graft/evm/firewood/reconstructed_state.go	Uses the new Copy() implementation from CopyTrie() for reconstructed account tries.
graft/evm/firewood/reconstructed_state_test.go	Adds a unit test verifying CopyTrie() returns an independent reconstructed trie.

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[alarso16]

The point of this was to fix a unit-testable issue with an API - doesn't this fully fix that issue? Will you add that to this PR?

[RodrigoVillar]

The point of this was to fix a unit-testable issue with an API - doesn't this fully fix that issue? Will you add that to this PR?

@alarso16 I added TestReconstructedCopyTrie() which tested the root cause of the bug (i.e inability to copy reconstructed account tries). To your point though, I've added another UT - TestFirewoodCopyTrie() - which calls both eth_estimateGas and eth_createAccessList under the reexecution path (which previously failed) and succeeds.

[alarso16]

You describe this test in relation to its fix, but it would be better to describe it relative to what functionality it actually needs: TestFirewoodModifiedStateRPC or something

[alarso16]

these don't make sense immediately, add a short comment

[alarso16]

subjective: separate subtest per block/transaction? it would help with debugging, but the nesting would likely feel unnecessarily deep