Prevent automatic Talkback "Detected text" announcement.

That announcement was pronounced because the focusable element
`id/device_container` had all its visible elements `id/title`
and `id/title_icon` marked with `importantForAccessibility=no`, so the
Talkback fell back to it's AI features to describe the element content.

1. Removed `importantForAccessibility="no"` by default from the title
element.
2. Set `focusable="true"` for the device container and
`focusable="false"` for title and subtitle to make screen reader
announce the device container as one entity as per
https://developer.android.com/guide/topics/ui/accessibility/principles#content-groups
3. When the seekbar is visible hide the rest of the content from the
accessibility tree with `updateContainerContentA11yImportance` method.

Flag: EXEMPT bugfix
Bug: b/374862206
Fix: b/374862206
Test: atest SystemUiRoboTests:MediaOutputAdapterLegacyTest,
    accessibility with Talkback.
Change-Id: Ifb3613af91ffb71e901e45903328b245e2a4b414