Describe the solution you'd like

See temporalio/features#331. Today, headers are not passed through the codec by default here like they are in .NET and Ruby and such. We should provide an opt-in somewhere to allow this.

Users using activities and such can just use the data converter w/ the codec, but inside workflows they can't easily, only the payload converter. Ideally all non-search-attributes go through codec, but we can't blindly flip this on.

Asks:

• Opt-in for all non-search-attribute payloads to go through codec (may need to be configured at client level)
  • Will have to update client and temporalio.bridge.worker.py's decode_activation and encode_completion
    • Bonus points if a payload visitor utility is created that does this and can also be used for other purposes, ref Full history decode utility features#468
• Confirmation via tests that all payloads go through the codec including activation/completion