[flexiglass] Simplify shade header highlight chips rendering.

By moving the highlight chips decision directly into the corresponding
composables, we achieve simpler and more robust code. Having the chip
determined statically by the parent composable (notifications or quick
settings shade), instead of independently listening to the STL state
flow in the view model, achieves more stable rendering and removes
unwanted artifacts during transitions (see b/413766503 for an example of
such an issue).

Bonus: Eliminate the "None" chip highlight.

Bug: 413766503
Bug: 397223606
Test: Manually by expanding and collapsing the shades and observing the
 chip highlights behave as expected.
Test: ShadeHeaderViewModelTest
Flag: com.android.systemui.scene_container
Change-Id: I0ccf95aec5f42b669599544f5dbb2a2c89230a61