feat(debug): align debug_trace* opcode tracer with execution-apis#762

[0xDevNinja]

Closes #12040

Changes

Aligns the default opcode (struct) logger output of debug_traceTransaction, debug_traceBlockByNumber and debug_traceBlockByHash with the standardized format from execution-apis#762. The same four fixes are applied to both struct loggers — the object-building GethLikeTxMemoryTracer and the direct-streaming GethLikeTxDirectStreamingTracer — so the streamed and in-memory responses stay identical:

1. error absent when no error occurred — was always serialized as "error": null. The GethTxTraceEntry.Error attribute now uses WhenWritingNull, and the streaming logger no longer writes a null error.
2. storage only on SLOAD/SSTORE entries, omitted when empty — previously a cumulative snapshot was copied onto every opcode entry, emitting "storage": {} on non-storage ops. The cumulative per-frame snapshot is now attached to an entry only when that opcode reads or writes storage, and omitted when there is nothing to report.
3. memory words 0x-prefixed bytes32 — TraceMemory.ToHexWordList() and the streaming memory path (including the zero-word padding) now prefix each word with 0x.
4. storage keys/values 0x-prefixed bytes32 — the storage snapshot keys and values are now 0x-prefixed.

Already compliant and unchanged: stack encoding, top-level field names (gas/failed/returnValue/structLogs), integer gas/gasCost, op opcode-name string, and the block-trace { txHash, result } pairing.

Verified the exact wire format against the conformance fixtures shipped in #762 (trace-block-memory-encoding, trace-block-storage-encoding, trace-block-storage-snapshot-timing).

Notes / scope

• This is a wire-format alignment only. Op-level storage capture remains gated by the existing IsTracingStorage flag (unchanged), so this PR does not change what data the struct logger collects, only how the emitted fields are shaped.
• Out of scope (tracked separately, per the issue): the genesis "not traceable" error path (debug_traceBlockByHash/debug_traceBlockByNumber returns [] for genesis block instead of an error #12038/add error in debug_traceBlock* if block is genesis #12039) and the memory-trace size options.

Types of changes

What types of changes does your code introduce?

• Bugfix (a non-breaking change that fixes an issue)
• New feature (a non-breaking change that adds functionality)
• Breaking change (a change that causes existing functionality not to work as expected)
• Optimization
• Refactoring
• Documentation update
• Build-related changes
• Other: Description

Testing

Requires testing

• Yes
• No

If yes, did you write tests?

• Yes
• No

Notes on testing

Updated the existing debug_trace* expectation fixtures (DebugRpcModuleTests) and the geth tracer unit tests (GethLikeTxMemoryTracerTests, GethLikeTxTraceConverterTests) to the new format. Added Streaming_tracer_emits_spec_aligned_wire_format, which drives the streaming struct logger over a real execution and asserts the absence of error/empty storage and 0x-prefixed memory words. All trace test suites pass.

Documentation

Requires documentation update

• Yes
• No

Requires explanation in Release Notes

• Yes
• No

The debug_trace* default struct-logger output now matches execution-apis#762: the error field is omitted when no error occurred, storage is emitted only on SLOAD/SSTORE entries (no more empty {}), and memory words and storage keys/values are 0x-prefixed.

[0xDevNinja]

Closing in favor of #12056, which already covers the same execution-apis#762 wire-format alignment and additionally fixes the op-level storage capture gating. No need for a duplicate.