Set the `stateDescription` for device list items in the CONNECTED state.

This improves the A11y announcement and allows the automation tests to
identify the connected elements.

Additionally, sets the default label for a group without a name to
"Group".

Fix: 408304744
Flag: EXEMPT trivial bugfix
Test: atest MediaOutputAdapterTest
Change-Id: Ie70636247e4dfb74801e5f4ee47143b1a5cfc47b