Fix NPE when dragging an app to bubble from taskbar

I shouldn't have removed the use of component utils to look
up the package name. I've added that back and modified the
test to work with it.

Flag: com.android.wm.shell.enable_bubble_anything
Test: atest WMShellRobolectricTests:BubbleTaskViewListenerTest
Test: manual - open an app, bring taskbar up, drag an app from taskbar
               to the bubble drop zone => observe that it works
Bug: 398847805
Change-Id: I4eff1faf4c49fd21538b0e77472416c83a04c765