Amend calendar view focus order

Moves the calendar contents view and slidable surface UI up in the
calender view's focus order (before the today button). Note that with
glanceables disabled, when calendar view is stand-alone bubble, it was
sufficient to ensure that date view gets initial focus, as the focus
would cycle from the slidable surface to the today button. With
glanceables, focus would not cycle withing the calendar view - it would
move into another glanceable bubble.

BUG=b:297186532

Change-Id: Ia539900fdd8e01e7ab21e0bd0380c22cd8301105
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4808994
Reviewed-by: Jiaming Cheng <jiamingc@chromium.org>
Commit-Queue: Toni Barzic <tbarzic@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1187649}