Make Edit mode internal in QuickSettingsScene

This removes the top level QSEditMode scene and replaces it with an
internal STL in QuickSettingsScene. Also, adds the appropriate
transitions.

Issues:
 * when swiping up from the bottom of edit mode, to dismiss to Gone, it
   dismisses correctly, but after performing this dismiss, next time QS
   is opened, it will crash (b/437886576)

Test: manual
Bug: 420960164
Bug: 437886576
Flag: com.android.systemui.scene_container
Change-Id: Ife70fae89919326a255a1e4ed3de89a4f3a1a19b