task: Rename gossip messages to be tx_id instead of tx_hash #4681
Description
We realized while reviewing another PR that the gossip messages should probably be updated to use TxID instead of TxHash.
Background for the original refactor: #4219
Yeah, I think all gossip messages (ObservationRequest, ChainGovernorStatus, and Observation) all use the outdated tx_hash as the name. I think it would be better to just rename all of those in a separate PR as I wouldn't want to touch the other message types.
Originally posted by @nvsriram in #4628 (comment)