synctl to show status and listening ports

This issue has been migrated from [#6599](https://github.com/matrix-org/synapse/issues/6599).

---

When running `synctl start` the server starts without letting us know that it's listening on TCP ports and which ones.
I'd find it helpful if synctl recalls the server's configured listening TCP ports when it starts.

I'd like to know what you think, whether it can become too verbose?

suggested behavior:
```bash
> synctl start
[...]
started synapse.app.homeserver('homeserver.yaml')
Listening on ::1:8008
Listening on 127.0.0.1:8008

> synctl status
Synapse is running with PID: 1337
Listening on ::1:8008
Listening on 127.0.0.1:8008

> synctl stop
> synctl status
No running Synapse process found
```