[Unity][Android] Remove 'Preload pages…' toggle from SyncAndServicesPreferences

This CL removes 'Preload pages…' toggle from SyncAndServicesPreferences,
moving it back to Privacy preferences page. It also reorders preference rows in
PrivacyPreferences if UnifiedConsent is enabled, putting 'Preload pages…' below
'Access payment methods' row. Title and summary of 'Preload pages…' in
PrivacyPreferences are also updated.

Bug: 925884
Change-Id: Ifcc58d71ecc6e22781ff5319a442e6293e086a22
Reviewed-on: https://chromium-review.googlesource.com/c/1472697
Reviewed-by: Theresa <twellington@chromium.org>
Commit-Queue: Boris Sazonov <bsazonov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#632831}
3 files changed