Implement mirroring

[cameri]

Add a setting to specify a list of relays to mirror. Allow the direction of the mirror to be configured. Allow the days to backfill to be configured. Keep track of the most recent event for each relay. Keep track from which relay the event came from? Allow mirroring to be throttled and a max queue size to be specified per relay. Allow whitelist/blacklist of pubkey and kind for each mirrored relay.