This removes most of the code used for polylith/API mode.
This removes the `/api` internal endpoints entirely.
Binary size change roughly 5%:
```
51437560 Feb 13 10:15 dendrite-monolith-server # old
48759008 Feb 13 10:15 dendrite-monolith-server # new
```
This adds Sytest and Complement coverage reporting to the nightly
scheduled CI runs.
Fixes a few API mode related issues as well, since we seemingly never
really ran them with Complement.
Also fixes a bug related to device list changes: When we pass in an
empty `newlyLeftRooms` slice, we got a list of all currently joined
rooms with the corresponding members. When we then got the
`newlyJoinedRooms`, we wouldn't update the `changed` slice, because we
already got the user from the `newlyLeftRooms` query. This is fixed by
simply ignoring empty `newlyLeftRooms`.
In an attempt to:
- make on-boarding a bit easier (`go test ./...` should now not need
additional postgres setup)
- get code coverage faster, not only scheduled at night
- test the `create-account` binary
