Rename *EventStub -> Sync*Event

[DevinR528]

I should also rename PduStub to SyncPdu right?

[jplatte]

I should also rename PduStub to SyncPdu right?

I wonder why we need that type actually. But yeah, it would be weird to still have Stub somewhere when "missing room_id" is otherwise signified by the Sync prefix everywhere.

[DevinR528]

In my find and replace looking around it seems they are used for federation endpoints.

https://github.com/ruma/ruma/blob/master/ruma-federation-api/src/membership/create_join_event/v1.rs

[jplatte]

Oh right. Yeah, it is weird renaming that since the room_id missing there has nothing to do with /sync, only with the room id being a path parameter rather than a body parameter. We should probably eventually find a way for that to work without the extra stub type, or with the stub type only being an implementation detail.

[jplatte]

I've cherry-picked the first commit, thanks for this! :)