AppSharing: Better handling of Work Profiles

This change improves the Work Profile use case in two ways:
1. When sharing is disabled for the profile, the Share App button is grayed out, and an appropriate message is displayed if the user taps it.
2. When sharing is enabled for the profile, it actually works.

Bug: 175159046
Bug: 210168826
Test: Manual (toggled DISALLOW_BLUETOOTH_SHARING via Test DPC on local device)
Test: m -j RunLauncherGoGoogleRoboTests ROBOTEST_FILTER=com.android.launcher3.AppSharingTest
Change-Id: Id7ba8efc587d0b94aa1f9b2004bf45254b39f992