Move components/sync/user_events into new components/sync_user_events

User events are now just another data type; no need to have the code in
the main sync components. The new location makes the relationship
clearer, and is consistent with others like sync_sessions,
sync_bookmarks etc.

Bug: 947443, 895340
Change-Id: I7787fad2ed634136aeb2be174f9bf47edf563df2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1583780
Commit-Queue: Marc Treib <[email protected]>
Reviewed-by: Jochen Eisinger <[email protected]>
Reviewed-by: Jan Krcal <[email protected]>
Cr-Commit-Position: refs/heads/master@{#656750}
46 files changed