Update media control colors for a11y

- Use new color scheme based on Material tokens
- Update scrim strength
- Lazy initialize in ColorSchemeTransition
- Set fixed text color directly XML styles/resources

Bug: 378848399
Bug: 378837284
Bug: 378837284
Flag: com.android.systemui.media_controls_a11y_colors
Test: visual, including with media_controls_ui_update and scene_container flags
Change-Id: I9b93a37fc6f286dea93a0b216ceec965292e4c01