Fix performance regressions

* Have the statusIcons always added to StatusBarIconController
  (attach/dettach) instead of when visibility changes. That prevents
  readding views and remeasuring.
* Introduce a specific variable for edit mode to control visibility.
  This makes it so that we don't have to rely on alpha (and it doesn't
  change with QS expansion).

Fixes: 266444213
Fixes: 265104777
Test: perfetto trace
Test: atest sysui-jank-custom
Test: atest LargeScreenShadeHeaderControllerTest
Change-Id: Ib8c3d1bcb1fb59f55c1c97a5b3966a2892b3f4b1