SearchFeatureProvider's context field is removed

SearchFeatureProvider was holding on to a context and
outlived the SettingsActivity, thus leaking the activity.
The context was passed into most methods, and thus it
makes more sense to pass it in to every method.

Bug: 33677967
Test: Run MakeSettingsRoboTests
Change-Id: Ia82f30e7e0b83587b4baeef28e81da6b8e4303fe