Remove WindowContainerController

It is no longer used. Reference removal:
root 31acb3f, stack 279f558, task 0e7aff9, activity 1ee84ea.

Bug: 80414790
Bug: 141248611
Test: go/wm-smoke
Change-Id: I23515d7ad5f218a70dfa05e5818a6ec2c2f857e8
8 files changed