Create BubbleTaskView

This is an initial no-op change that introduces BubbleTaskView, which is a class that wraps a TaskView and a listener.

This change moves the creation of TaskView outside of the bubble expanded view class, and instead passes it a TaskView instance.

In follow up cls BubbleTaskView will be stored in the Bubble class so that we can keep the TaskView when switching between floating and bar modes. See ag/25863141 for a prototype of how this would work.

Bug: 316358859
Test: atest BubbleTaskViewTest
Change-Id: Idc8caa256f9c8e408d7a62a0db40dc717ea5ea45