[CrOS MultiDevice] Prepare settings UI infrastrcture for feature data.

This CL replaces some data types we had thought would be important for
displaying the multidevice settings page that wound up being redundant
with the data types we will need to receive individual feature updates
from the multidevice service.

Bug: 824568
Change-Id: I33b70cba332dec8cf7726630ccbf57bcf62b8655
Reviewed-on: https://chromium-review.googlesource.com/1173658
Commit-Queue: Kyle Horimoto <khorimoto@chromium.org>
Reviewed-by: Hector Carmona <hcarmona@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583724}