[docdb] Master falling behind does not get automatically remote bootstrapped

[bmatican]

Jira Link: DB-1842
Currently, if a master falls behind to the point that the leader no longer has logs, or its follower unavailability window passes (default 15m for both), it would require manual intervention to remove it from the quorum and add it back.

At the raft level, we have this flag to control w/e or nor to evict failed followers: evict_failed_followers. This is disabled for masters though, as there is no automated mechanism for them to be added back into the quorum!

Moreover, until #2007 is resolved, the current steps of issuing a remove, followed by an add, require that in between, we actually wipe the master data and start back the master in shell mode (empty master_addresses flag).

Ideally, we'd have some mechanic through which we would automatically trigger a remote bootstrap for the master, if it comes back after the default 15m window.

cc @iSignal @hectorgcr