[CrOS MultiDevice] Move appropriate CryptAuth files to DeviceSync.

This is part of the ongoing effort to clean up the directory structure
of multi-device code. The files moved are only relevant to the
DeviceSync service, so they belong within the service implementation.

See go/multidevice-directory-structure-cleanup for details.

Bug: 912743
Change-Id: Icce398a4aa93110fbd790c364bba29bf461a83e4
Reviewed-on: https://chromium-review.googlesource.com/c/1372648
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Matt Menke <mmenke@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Ryan Hansberry <hansberry@chromium.org>
Commit-Queue: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616056}
133 files changed