Allow bots to edit messages sent by a webhook owned by the application

[quirky-bluejay]

In #2164 (comment) it was mentioned this was a possibility.

This would mean that messages sent by application owned webhooks would be editable by the bot user (PATCH and DELETE on /channels/{channel.id}/messages/{message.id}.

Currently messages sent by webhook can only be edited by that webhook. This means that in order to edit a message the webhook that was used to send the message can't be deleted, which could happen in a few ways, if the bot user (if there was one) in that server was removed and added again, someone deleted it, etc.
The ability to always be able to edit a webhook message would be useful for long lived updated messages (for example for info, roles, etc).

Possible Alternatives

Allowing an application webhook to edit any message in the same channel that was also sent by a different and / or deleted webhook owned by the same application.

Persisting the application owned webhooks (in an inactive state) when deleted