Update widget predictor to apply prediction filter

When enough widgets are not passing the filter, additional randomly
 selected widgets are added.

The count to decide whether to add more is a configuration, so that,
if some OEMs don't want any suggestions, can override the value to 0.

Bug: 356127021
Flag: com.android.launcher3.enable_tiered_widgets_by_default_in_picker
Test: Unit tests
Change-Id: Iffa8619149a1a4b468d367fc7bbee381be59469d