ACP-25 VM Application Errors

[joshua-kim]

Support VM defined application errors. Introduces a new p2p message type. #25

[joshua-kim]

1. I think AppError sounds better than AppRequestFailed but AppRequestFailed is the current name of the VM interface's function that's invoked in timeout. We could consider using the AppError name instead and just rename the VM signature.
2. Some follow-up ideas could be to score VMs, and to incentivize sending AppRequestFailed messages by deducting more score for network timeouts as opposed to an application defined error.

[patrick-ogrady]

1. I agree. AppRequestFailed sounds like a class of errors (could be timeout or explicit error).
2. I think this should be left to the VM to determine based on the content of the message. Some messages would be OK to fail IMO.

[joshua-kim]

Rename PR: ava-labs/avalanchego#2321

[patrick-ogrady]

Short circuit timeout-based errors wherever we can!

[avalanche-foundation-admin]

This conversation has migrated to the official ACP discussion: #39