Add scrolling to QS

This will allow QS to scroll when it's taller than its container. A few
notes:

* The ShadeHeader scrolls with the same Y, that's following current
  behavior.
* Fixes an empty list on composition of QQS. This prevents a frame where
  the height is just the padding and therefore
  QuickSettingsControllerImpl has the wrong height for fling.
* Forces height of the footer, so it won't be squished when it almost
  fits. Instead, the container will become scrollable.

Test: manual, using larger display size
Bug: 353254131
Flag: com.android.systemui.qs_ui_refactor_compose_fragment
Change-Id: I9a13aefebd2fd6be93e1d5eafbf44f8a1c6487b4