Cleanup cloud reporting policies

Delete three policies that causes issue or confusion on Admin Console.
ReportMachineIDData
ReportUserIDData
ReportVersionData

Remove policy migrator as it's not used by local reporting and
cloud reporting policies are going to be decoupled from the extension
policies.

Tbr: karandeepb@chromium.org
Change-Id: I5fcfa665aee3899dbd0d446427af2c4821de13fc
Reviewed-on: https://chromium-review.googlesource.com/c/1351288
Commit-Queue: Owen Min <zmin@chromium.org>
Reviewed-by: Julian Pastarmov <pastarmovj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611776}