Refactor grant dialog to make more themeable

Layouts for the permission grant dialog have been consolidated into
res/layout/grant_permissions.xml.

The layout now uses the Dialog.Alert theme to be more consistent
with other alert dialogs.

Custom animations removed.

Added RRO policy to restrict customization.

Test: Appearance looks correct & fuctionality isn't changed
Change-Id: I7ee1d76b3dfa43d783d36835cc1fc7ccfd22d017