Should instantiate ReshardingMetrics object with the persisted data

Tracked quantities in the ReshardingMetrics class:

• runningOperation time interval (c)
• ** opStatus (d, c, r) always set to running.
• copyingDocuments time interval (r)
• documentsToCopy (r)
• documentsCopied (r)
• bytesToCopy (r)
• bytesCopied (r)
• applyingOplogEntries time interval (r)
• oplogEntriesFetched (r)
• oplogEntriesApplied (r)
• // inCriticalSection time interval (c)
• // writesDuringCriticalSection (d)
• donorState (d)
• recipientState (r)
• coordinatorState (c)

d = donor
r = recipient
c = coordinator