Deletes the forwarding headers in base/prefs.

Updates the remaining users of base/prefs includes to use components/prefs.
Sort headers in updated files.

Move PrefServiceFactory out of the base namespace. Update users.

Update all preprocessor stuff in components/prefs to change BASE_PREFS_ to
COMPONENTS_PREFS_.

Add components/prefs to DEPS file of directories where checkdeps fails after
the update.

BUG=583034
Reland of http://crrev.com/1662523004#ps40001 with fix.
TBR=estade@chromium.org

Review URL: https://codereview.chromium.org/1668463002

Cr-Commit-Position: refs/heads/master@{#373197}