[Sync] Rename syncable_prefs to sync_preferences.

Pretty mechanical CL:
- Moved files and ran mass-rename.py
- String-replaced "syncable_prefs" with "sync_preferences"
- String-replaced "SYNCABLE_PREFS_USE_POLICY" with "SYNC_PREFERENCES_USE_POLICY"
- Fixed a couple lints inside sync_preferences
- Ran formatter

BUG=659265
TBR=jam

Review-Url: https://codereview.chromium.org/2459823002
Cr-Commit-Position: refs/heads/master@{#428391}
diff --git a/chrome/browser/BUILD.gn b/chrome/browser/BUILD.gn
index 8e01820..d9e0de9 100644
--- a/chrome/browser/BUILD.gn
+++ b/chrome/browser/BUILD.gn
@@ -1388,8 +1388,8 @@
     "//components/supervised_user_error_page",
     "//components/sync",
     "//components/sync_bookmarks",
+    "//components/sync_preferences",
     "//components/sync_sessions",
-    "//components/syncable_prefs",
     "//components/task_scheduler_util",
     "//components/tracing:startup_tracing",
     "//components/translate/content/browser",
@@ -4152,7 +4152,7 @@
     "//components/sessions:test_support",
     "//components/subresource_filter/core/browser:test_support",
     "//components/subresource_filter/core/common:test_support",
-    "//components/syncable_prefs:test_support",
+    "//components/sync_preferences:test_support",
     "//components/user_prefs/tracked:user_prefs_tracked_test_support",
     "//content/test:test_support",
     "//google_apis:test_support",