[CrOS MultiDevice] Refactor shared MultiDevice setup flow resources.

The MultiDevice setup flow uses several HTML/JS resources to render the
setup flow dialog. Previously, these files were added directly to the
data source for chrome://multidevice-setup.

Now that this UI is being shared between both chrome://multidevice-setup
and chrome://oobe, the resources are moved to a shared location; namely,
//ui/webui/resources/cr_components/chromeos/multidevice_setup. They are
now served from
chrome://resources/cr_components/chromeos/multidevice_setup/*.

Bug: 884041
Change-Id: Ia69c27875a9d3600006c4220f498acc5a2aef7be
Reviewed-on: https://chromium-review.googlesource.com/1232334
Commit-Queue: Kyle Horimoto <khorimoto@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#593378}
48 files changed