Expose replication status on the /metrics endpoint

[nunodio]

Did you search GitHub Issues and GitHub Discussions First?
Yes. Issue #4629 is related but not address the replication metrics requested here.

Is your feature request related to a problem? Please describe.
Having replication metrics available on /metrics will allow teams to configure alerts so they can be notified when replication is not working as expected.

Describe the solution you'd like
Dragonfly expose the metrics master_link_status, master_last_io_seconds_ago and master_sync_in_progress and slave_repl_offset on /metrics endpoint.

Describe alternatives you've considered
N/A

Additional context
N/A