[sync] Fix value logged in some metrics

Incorrect values were logged in Sync.BatchUpload.Requests and
Sync.UnsyncedDataOnSignout. This CL fixes that.

OBSOLETE_HISTOGRAMS=Sync.BatchUpload.Requests, Sync.UnsyncedDataOnSignout are replaced by Sync.BatchUpload.Requests2, Sync.UnsyncedDataOnSignout2 respectively because they reported incorrect values.

Bug: 1483204,1496731
Change-Id: I6c8c2ebc0b9a41102733b008910eea750f7b222f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5046560
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Commit-Queue: Ankush Singh <ankushkush@google.com>
Reviewed-by: Rushan Suleymanov <rushans@google.com>
Reviewed-by: Jérôme Lebel <jlebel@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1227882}