[DO NOT MERGE] Unify QS Headers in a ConstraintLayout

This is a POC and is missing several features:
* Tight integration with the other surfaces to set margins
* Expansion animation from QQS into QS
* Privacy indicators

To enable:
adb shell am broadcast -a com.android.systemui.action.SET_FLAG --ei id
501 --ez 1

Test: manual
Bug: 204204226

Change-Id: I5b2d5f5880ceff1adb1e4365cde15171c5c15d38