Android Auto: Fix suggestions and page update notifications

Description

This MR has two changes:

1. onGetRoot returns suggestions to the Google quick search box client to populate the 'For You' section of Android Auto even though the EXTRA_SUGGESTED root hint is no longer used. We still support the hint if others want to use it, or if Android Auto starts recognizing it.
2. Page change notifications are sent for specific mediaIds (URIs in our case) as the new Android Auto UI eagerly traverses top level tabs and caches the contents! Previously we relied on capturing the id of the last page retrieved, which worked because pages were accessed based on user interaction; however, that now only applies to lower level child pages and a single event type.

Resolves

Fixes: #3163 (closed)