[Feature]: add authz MsgRevokeAll message

[arlai-mk]

Summary

The authz module currently requires a user to revoke grants one by one, providing the grant message, the grantee, and the granter.
There is no option to revoke all grants at once, which could be useful in case of a wallet compromise.

I would like to suggest adding a MsgRevokeAll message for this purpose.

Problem Definition

This idea come from a case that I've been asked to investigate, where an attacker, right after enticing his victim to sign a MsgGrant authorization, created grants for 2000 other addresses under its control (one example tx: https://www.mintscan.io/cosmos/tx/5C21BC64CF0FF8502DCF1DD623973FDB939B3519259881135E5861CC5BA16157?height=19607416).

As revoking grants needs to be done one grant at a time (you need a UI to list them and then revoke them all), it makes it impossible to protect yourself after authorizations have been granted to 2000 addresses.

This has already been discussed in this thread, now creating a separate issue on @julienrbrt advice.

Proposed Feature

The MsgRevokeAll message would loop through all grants from a specific granter and Delete them all.

[kien6034]

hi guys, can I work on this issue?

[julienrbrt]

Yes, thank you!