Infrastructure for showing instant app metadata in app header

This adds infrastructure for displaying the following instant app
metadata in the app header:
-Developer title
-Maturity Rating icon and description string
-Monetization notice (eg ads and/or in-app purchases)

Bug: 35098444
Test: includes new robotests in AppHeaderControllerTest.java
Change-Id: Ifadfedc7f5f349869d6616aeb5ed19eb2b22a038