Implemented taskbar application icon drop onto the bubble bar drop zone.

Added logic to create a new application bubble in the bubble bar
when dragging and dropping taskbar application icon.

Bug: 388894910
Flag: com.android.wm.shell.enable_create_any_bubble
Test: atest BubbleControllerTest
Test: Manual. Drag an app icon from the taskbar while inside the
application to any bubble bar drop zone and drop it there. Observe
that a new application bubble is added and the bubble bar expands,
showing the newly added bubble content in the expanded view.
video: http://recall/-/gx8ASgewUeUS3QYohfrd1J/erIYLNwEjzD0T5konPIdY6

Change-Id: I2b17261c05be456d606cb5fffe8151b1d9b5c70c