The `get_rooms_paginate` DB queries are slow

The `RoomWorkerStore.get_rooms_paginate` DB store method contains some slow SQL queries. This method is currently only called when hitting the [List Room Admin API](https://element-hq.github.io/synapse/latest/admin_api/rooms.html#list-room-api). The current codebase contains this query:

https://github.com/element-hq/synapse/blob/f1c4dfb08b530f2bfaf9c6723ce69ccd231a3370/synapse/storage/databases/main/room.py#L703-L723

Due to the two `INNER JOIN`s, the statement [takes about 700ms to execute](https://github.com/element-hq/synapse/pull/17276/files#r1633079477) on matrix.org (and this is after caching, as I ran the statement once before attempting to `ANALYZE` it).

https://github.com/element-hq/synapse/pull/17276/files#r1631162300 added a similar set of `INNER JOIN`s to the `count_sql` query.

These joins are necessary to access metadata about rooms, which is spread across multiple tables. For instance, the `rooms` table contains an `is_public` column, which allows for filtering room results based on whether a room is published in the public room directory.

Can we consolidate this information into a single table somehow? Or is there a faster way to access information across multiple tables than `INNER JOIN`s?