Remove TaskWindowContainerController & TaskWindowContainerListener (44/n)

Rename the TaskWindowContainerControllerTests to TaskTests and keep the
tests still make sense after removing the container.

TaskRecord and Task hold each other as a member. TaskRecord will create
Task while constructing.

Test: atest WmTests
Test: go/wm-smoke
Bug: 80414790
Change-Id: Iac9dc9cafdbb22ddbe325f8ff178874f3790f251