RoomListService's `filter_deduplicate_versions` does not remove a tombstoned room after joining its successor

@Hywan is already working on this.

Since Dec 26, 2025.

In the [Robrix](https://github.com/project-robius/robrix) client, I am using the `RoomListService` like with fairly normal filters:
```rust
// By default, our rooms list should only show rooms that are:
// 1. not spaces (those are handled by the SpaceService),
// 2. not left (clients don't typically show rooms that the user has already left),
// 3. not outdated (don't show tombstoned rooms whose successor is already joined).
room_list_dynamic_entries_controller.set_filter(Box::new(
filters::new_filter_all(vec![
Box::new(filters::new_filter_not(Box::new(filters::new_filter_space()))),
Box::new(filters::new_filter_non_left()),
Box::new(filters::new_filter_deduplicate_versions()),
])
));
```

This only works as expected for old tombstoned rooms whose successors have already been joined _before_ the client first starts. However, if I join the successor room while the client is running (i.e., after starting the RoomListService), the old room is not removed by the RoomListService and will still be incorrectly shown, meaning that the filter(s) are being ignored.

cc discussion from the Matrix Rust SDK room: https://matrix.to/#/!2GTp0cl8dqhPideYm7pKNABc2m2VqBZz7pVX_UUlijE/$DTaxmpC6_OTrSk8-4bmBAyZNd9bw2AdkmQHsaeAbqNI?via=matrix.org&via=element.io&via=envs.net