P2P App Sharing: Gray out disabled SystemShortcut

The Share App system shortcut is disabled for apps that are deemed unshareable. This updates the UX to gray out the shortcut instead of hiding it. When the user clicks on the grayed out shortcut, a Toast message is displayed. This update also enables the shareability check.

In order to properly gray out the shortcut, this also fixes a bug with BubbleTextView in which ColorStateLists weren't applied correctly.

Bug: 202556634
Bug: 204495363
Test: Manual (observed UX on Wembley device in regular and dark themes)
Test: m -j RunLauncherGoGoogleRoboTests
Change-Id: Ieb04baf8c9cb9d325119cb97fceb96f2fc5a62ff