fix: allow empty ethereum trace output

[ppca]

#1088
Fix Ethereum bidirectional response extraction for successful contract calls that return no data.

Some RPC providers omit output from debug_traceTransaction call frames when the traced contract call returns no bytes, rather than returning "output": "0x". This caused the Ethereum indexer to fail output extraction and drop the ExecutionConfirmed event, leaving bidirectional requests pending.

Changes:

• Represent trace results with TraceOutput::{NotTraced, Output, NoReturnData}.
• Treat missing output as no return data only when the trace result is a valid call frame.
• Allow no-return-data contract calls only when output_deserialization_schema declares no return values.
• Preserve errors for malformed traces, null trace results, and non-empty output schemas.
• Synthesize the existing success/default response for void-return calls, including Hydration’s Borsh bool response.
• Replace a Borsh schema assert! with a returned error to avoid indexer panics on malformed response schemas.
• Add a TODO for surfacing unrecoverable extraction failures beyond logs