`synapse.api.auth.Auth` cleanup: make permission-related methods use...

`synapse.api.auth.Auth` cleanup: make permission-related methods use `Requester` instead of the `UserID` (#13024)

Part of #13019

This changes all the permission-related methods to rely on the Requester instead of the UserID. This is a first step towards enabling scoped access tokens at some point, since I expect the Requester to have scope-related informations in it.

It also changes methods which figure out the user/device/appservice out of the access token to return a Requester instead of something else. This avoids having store-related objects in the methods signatures.