Add getShareTargets() to ShortcutServiceInternal and get caller's user ID from...

Add getShareTargets() to ShortcutServiceInternal and get caller's user ID from AppPredictionSessionId

Previously, the caller's user ID was got from Binder. But
AppPredictionManager clears caller's identity. The only way to get the
caller's user ID is to get it from session ID.

Bug: 146522621
Test: atest com.android.server.people.data.DataManagerTest
Test: atest com.android.server.people.data.ShareTargetPredictorTest
Change-Id: Ia0dc35879084110849e06e919ff3b3c7241c46fd