Add Start Activity API for TileServices

This API allows developers to add a pendingIntent to a CustomTile, which
will allow the tile to start a new activity.

There are two ways of using this functionality:
1. Call TileService#startActivityAndCollapse(pendingIntent) to
   immediately start a new activity

2. Set a pendingIntent in advance with
   Tile#setActivityLaunchForClick(pendingIntent), and the activity will
   start when the user clicks on the tile

Bug: 241766793
Test: atest CustomTileTest
Test: atest TileServicesTest
Change-Id: I07ad73ae468eed7a03202babfaeab271d4f7f3ae