fix issue 201: Syncing time estimation is not accurate

[ping-ke]

issue 201: #201

The data syncing and filling-empty speeds may vary significantly, so calculating their respective times would provide a more accurate estimate. This change split the state report into two parts -- sync process and fill empty process.

How to test:
Run the es-node and see the sync state like the following.

INFO [02-05|04:23:44.659] Storage sync in progress                 progress=0.50% peerCount=6 tasksRemain=1@32 blobsSynced=5824@728.00MiB blobsToSync=1,150,778 timeUsed=2m32s etaTimeLeft=8h20m34s
INFO [02-05|04:23:44.659] Storage fill empty in progress           progress=0.54% tasksRemain=1@30 emptyFilled=16368@2.00GiB  emptyToFill=3,021,334 timeUsed=2m32s etaTimeLeft=7h47m37s