Log screen events for blocked call fragments

* Add blocked number screen types to Logger
* Log screen views for SearchFragments in DialtactsActivity
rather than in onStart, to avoid double logging for some
fragments (e.g. children of RegularSearchFragment)
* Log screen view for call log context menu (where the block
number action appears

Bug: 25288435
Change-Id: I4ebf1410f93afb37d20be2cc57f933e5d635cfb6