rpc/jsonrpc: source executionWitness codes from pre-state reads

[awskii]

Problem

debug_executionWitness's codes field is built from RecordingState.GetAccessedCode() — every bytecode reached via GetCode/GetCodeSize during execution, including contracts created in-block. That matches Geth's witness.AddCode semantics, but EEST fixtures (and the canonical stateless-witness format) are filled by Reth's Canonical mode, which only emits bytecodes loaded from pre-state by codehash and excludes in-block-created code. A stateless verifier re-derives created code by replaying the block, so emitting it is redundant over-inclusion.

This is the dominant remaining source of codes-witness divergence: a per-block +1 (sometimes +2) over-inclusion.

Fix

Source the witness codes from GetPreStateCode() (inner-reader / pre-block reads only) instead of GetAccessedCode(). One-line change plus a corrected doc comment.

The stateless verifier (witnessStateless.ReadAccountCode) already resolves in-block-created code from codeUpdates (written during re-execution) before consulting the witness codeMap, so the verify path does not regress.

Evidence (EEST zkevm@v0.4.0 corpus, ~2,881 fixtures)

Metric	before (main codes path)	after
Pass rate	94.6%	98.5%
codes witness mismatches	924	11
stateless-exec failures	0	0
state-root mismatches	0	0

A static sweep over all 924 pre-fix codes mismatches found that 100% (925/925) of the over-included bytecodes were absent from pre-state — every one was created in-block (278 survive into post-state, e.g. cross-tx selfdestruct-to-self and in-block EIP-7702 delegation markers; the rest transient). Zero regressions vs the prior best; 111 newly-passing fixtures.

The residual 11 codes mismatches are EEST eip8025_optional_proofs/witness_validation_codes/* negative-validation fixtures (deliberately truncated/padded witnesses that test a verifier's rejection path), plus one same-codehash edge case (witness_codes_create_same_hash_then_read).

Notes

• This supersedes the narrower EIP-6780 transient-code filter approach (it covered only the deleted ∧ ∉ pre-state subset; the pre-state rule covers all in-block-created code).
• RecordingState.GetAccessedCode() / OnCodeAccess are now unused by the witness builder but remain wired into the IBS code-read path; removing that machinery is deferred to keep this diff surgical.

Refs #21307.