eth/catalyst: add initial OpenTelemetry tracing for Engine API newPayload

[jrhea]

⚠️ Note

This PR depends on generic OpenTelemetry tracing being available in the JSON-RPC server. That work can be tracked in PR #33452. Once it lands, this PR can be rebased and updated to build Engine API specific spans on top of the generic RPC tracing.

No further review needed at this time.

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This PR adds initial OpenTelemetry tracing to the Engine API, focusing on engine_newPayload*.

Scope

• Engine API only
• Root spans are created at Engine API entrypoints (NewPayloadV*)
• Child spans for payload decoding and block import

Notes

• Currently uses a synchronous exporter with AlwaysSample (temporary).
• No CLI flags or lifecycle shutdown wiring yet

Questions

• For eventual per-transaction spans under engine_newPayload, should we adapt the existing core/tracing.Hooks (e.g. OnTxStart / OnTxEnd) into OpenTelemetry spans?
• Should validation failures (e.g. “withdrawals not supported in V1”, etc.) be recorded as span errors?
• What sampling methodology should we use?

Validation

Tested locally using SigNoz. Example trace from engine_newPayload: