Synapse doesn't backfill missing events when rejoining a room later

This issue has been migrated from [#15717](https://github.com/matrix-org/synapse/issues/15717).

---

### Description

If I'm the only user from my home server in a room (with more users from other severs),
stays there for a while and get's a lot of events,
then leave the room,
then rejoins the room a few days later,
I'm missing the events in the room between the point where I left the room up to the point I rejoined the room.

Synapse does not backfill those events.

### Steps to reproduce

- As the only user from your home server, join a room with other servers
- Stay in the room for a while to get events in the room ( like messages, joins etc)
- Leave the room for a while (so long as to there being new events in the room)
- Rejoin the room
- See that the missing events doesn't get backfilled

You will see something like this:
* you joining the room
* messages
* messages
* messages
* you leaving the room
------
missing events you will not see
--------
* you joining the room
* new messages
* new messages
[homeserver_logs.tar.gz](https://github.com/matrix-org/synapse/files/11649606/homeserver_logs.tar.gz)

I have reported this before years ago but I shut down that server before Matrix team started to investigate, and when they looked at the bug they closed it because I wasn't active any more. So this is an old bug and not something newly introduced.

### Homeserver

sinnesro.se

### Synapse Version

{"server_version":"1.84.1","python_version":"3.9.2"}

### Installation Method

Debian packages from packages.matrix.org

### Database

Single PostgreSQL, never used SQLite, never restored from backup

### Workers

Single process

### Platform

Debian 11 latest updated
Running in an LXD

Intel Core i5 12th gen, 16 GB RAM, 256 GB SSD

### Configuration

_No response_

### Relevant log output

```shell
I have included my home server logs earlier in the bug report because I don't know what is relevant to show here.
```

### Anything else that would be useful to know?

_No response_