Minor Copy/Paste overlay UI edits

- update background color of text view to match buttons
- add padding to right edge of edit text activity TextView
- add ellipsis when text is cut off in preview

Bug: 223845368
Fix: 223845368
Bug: 223965587
Fix: 223965587
Bug: 223829956
Fix: 223829956
Test: manual (visual changes; tested in light and dark modes)
Change-Id: Ibcb276c34e402687a7954887d0574e60501d178b