Sliding Sync: Make sure we get up-to-date information from...

Sliding Sync: Make sure we get up-to-date information from `get_sliding_sync_rooms_for_user(...)` (#17692)

We need to bust the `get_sliding_sync_rooms_for_user`
cache when the room encryption is updated and any
other field that is used in the query.

Follow-up to https://github.com/element-hq/synapse/pull/17630

- Bust cache for membership change (cross-reference
`get_rooms_for_user`)
- Bust cache for room `encryption` (cross-reference
`get_room_encryption`)
- Bust cache for `forgotten` (cross-reference
`did_forget`/`get_forgotten_rooms_for_user`)