Implement design on privacy dialog

* Implement margins and styles
* Change tappable region to whole row
* Implement a11y for whole row

Also, fix a bug with background window that would show black on some
devices instead of transparent.

Bug: 178093014
Fixes: 178616173
Test: manual
Test: atest PrivacyDialogTest
Change-Id: If03fcd75970a724f8209596b75640c5618b3b9c2