Make Change Key for Permissions v2 Audit Log consistent

[ckohen]

Originally discussed in #4841 and #4919.

⚠️ Unfortunately this has been stalled long enough so it would be a breaking change.

The idea here is to get the key for application commands permissions update to be something other than a snowflake. It makes it significantly harder (read: impossible) to type these entries as strictly as we could before. It's basically typing the key as a String now and leaving it at that. If you do use that, you can no longer identify the type of the values by the key as every key matches the one for the permissions update entry so you end up with a union of the inner types.

This screams the need for another special key like $add and $remove that's just for this entry. (Note: not reusing these keys)

But what about the id???? No need to worry about that, its already in the new / old value object. Oh, and that object also contains the type of that id, so most devs are probably checking that inner payload anyways (aside from the obvious check of the permission property) in order to more quickly and correctly find the channel, role, or user that is trying to be identified.

[erkinalp]

What about update events themselves getting IDs? That would allow logging the event ID as the change key, instead of the ID of the updated object.