Recover Persistent database DB by DB and not record by record

Recover Persistent database DB by DB and not record by record

Add a new tunable that changes the mode how persistent databases are recovered.
RecoveryPDBBySeqNum

When set to 1, persistent databases will be recovered in whole from the node which
has the highest "__db_sequence_number__" record.
This record is managed by samba for those databases where we do persistent writes and have
inter-record relations.
For these databases we do not want the usual "blend records from all nodes based
on individual record RSN" but instead a mode where we pick one instance of the persistent database.

If no node was found with a "__db_sequence_number__" record at all, we fail back to the original "recover records independently based on record RSN".
Some persistent databases do not contain record interrelations and as such does not
contain this special record at all.