Code cleanup and visual polish for hybrid views

These views (the single line children of a group when it is collapsed) were missing some pretty basic polish pieces.  This CL:
* Removes unnecessary styles (the alternative theme was removed years ago) that also required an extra context allocation.
* Apply the themed text colors to the text views.  Leave colors alone (e.g. use the un-themed defaults) if theme colors cannot be resolved.
* Ensure the "conversation sender name" text view translates vertically with the title and text when it fades out.

Test: manual expansion
Bug: 236252445
Change-Id: Ib578eeffa5c78a0016ba818fa0273daa54bee748