Polish unfocused dimming feature

[Tyriar]

This is a meta issue to track what remains after the August testing round.

• Integrate the feature more deeply to improve maintainability Editor dimming should be a core workbench feature #191757
• Various editors not dimming
  • Running extensions editor is not dimmed #191744
  • Workspace trust editor is not dimmed #191743
  • Unclear what part of the editor is dimmed #191608
  • iframes
    • Notebooks are not dimming #191615
    • Webviews don't respect accessibility.unfocusedViewOpacity #189650
• Support unfocused dimming of all workbench components like output and debug console #191616
• Unfocused editors should regain focus (be un-dimmed) on scroll #191671
• Does not regain focus on minimap #191714
• editor should not be dimmed when navigating search results #190102