Previously we were mashing everything together as RoomAccountDataEvent,
even the global events. This technically worked, because of the hidden
custom fields on the ruma event types, but it's confusing and easy to
mess up. Separate methods with appropriate types are preferable.
This allows us to use the `ruma_route` convenience function even when we
need to add our own hacks into the responses, thus making us less
reliant on Ruma.
This change is fully automated, except the `rustfmt.toml` changes and
a few clippy directives to allow specific functions with too many lines
because they are longer now.
