[identity] dedup "unexpected message data" tonic message

Summary:
there are a lot of tonic status messages that need to be converted to snake_case and dedup'd.

i've arbitrarily broken this work up into chunks to make it easier to review

Test Plan: git grep for the old status messages, change client error handling where needed

Reviewers: bartek

Reviewed By: bartek

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D12401