Add hotword in Assistant OptIn flow

Bug: b/78190629
Test: Manual Test
Cq-Include-Trybots: luci.chromium.try:closure_compilation
Change-Id: Ic87f99c00c51bbb92c036e5cb954cffe79c43f48
Reviewed-on: https://chromium-review.googlesource.com/1144057
Commit-Queue: Yue Li <updowndota@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576930}
4 files changed