Allow Shortcuts to be started on ActivityView

We're doing some experiments with using shortcut info to produce bubbles
instead of bubble metadata, shortcuts can only be launched via
LauncherAppsService, not an intent so we need a new method on ActivityView.

Test: manual with sysui CL ag/9617215:
      1) enable shortcut-created bubbles
      2) send a notification with shortcutId attached
      3) expand that bubble

Bug: 143173197
Bug: 138116133
Change-Id: I4d621ce703a40512588b9bd834dece9fe2ba9d8a