Use subprocedure of Proc V2 for snapshot in BackupProcedure

Currently for SNAPSHOT_TABLES stage, we loop through the tables and take snapshot for each table.
If the master restarts in the middle of this stage, we would restart taking snapshot from the first table.

This issue would use subprocedure for each snapshot so that we don't need to take snapshot for the table(s) whose snapshot is complete before the master restart.