[AF] Clean-up autofill_sync_bridge_util

This CL cleans-up a util file doing three changes:
 - renames functions to make clear which are used for wallet data and
   which for wallet metadata;
 - fixes the behavior for some functions (only used from the bridge's
   GetAllDataForTesting()/GetAllDataForDebugging()) to make them
   consistent with the real production code-paths;
 - moves functions solely used from the data bridge to its anonymous
   namespace.

Similar clean-up for metadata functions from autofill_sync_bridge_util
will be done by a separate CL.

Bug: 853688
Change-Id: I44df9fc0e60e5d7272c2ebc2005cf608dd4a86b4
Reviewed-on: https://chromium-review.googlesource.com/c/1402762
Commit-Queue: Jan Krcal <jkrcal@chromium.org>
Commit-Queue: Sebastien Seguin-Gagnon <sebsg@chromium.org>
Reviewed-by: Sebastien Seguin-Gagnon <sebsg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#621162}
4 files changed