DO NOT MERGE: Add configurable default setting for assistant componentname

By requiring an explicit default setting, it eliminates all ambiguous
states where a disambiguation would normally be shown. With this
change in place, at no point should a disambiguation be shown.

Test: manual
Bug: 111603898
Change-Id: Id39fdf700ed4ef08ebbc333b5452223430ac2e48
Merged-In: Id39fdf700ed4ef08ebbc333b5452223430ac2e48