Fix incorrect default browser summary.

- move the logic to retrieve browser candidates with unique package name
from default browser picker to the controller, so that both uses the
same logic to get the candidate list. When there is only 1 package that
can handle the web but it has multiple resolved activities, it should
be considered as the only app, and hence be set as default.

Change-Id: I945bcef3f7de586b19f65ceada3abf7addb0b26e
Fixes: 109882811
Test: make RunSettingsRoboTests