There can be rare situations where errors seen in bucket metadata
load on startup or subsequent metadata updates can result in missing
replication remotes.
Attempt a refresh of remote targets backed by a good replication config
lazily in 5 minute intervals if there ever occurs a situation where
remote targets go AWOL.
to track the replication transfer rate across different nodes,
number of active workers in use and in-queue stats to get
an idea of the current workload.
This PR also adds replication metrics to the site replication
status API. For site replication, prometheus metrics are
no longer at the bucket level - but at the cluster level.
Add prometheus metric to track credential errors since uptime
to avoid relying on scanner-calculated replication metrics.
This will improve the accuracy of the replication stats reported.
This PR also adds on to #15556 by handing replication
traffic that could not be queued by available workers to the
MRF queue so that entries in `PENDING` status are healed faster.
This PR changes the handling of bucket deletes for site
replicated setups to hold on to deleted bucket state until
it syncs to all the clusters participating in site replication.
