add multi-window support to accessibility system

[kryksyh]

• Adds app-wide accessibility root, which owns all windows within the same process
• AccessibilityConfiguration was removed since it is no longer needed

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• Each commit's message describes its purpose and effects, and references the issue it resolves
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[igorkorsukov]

What confuses me is:

• This reveals the logic for enabling accessibility, i.e. the logic described here is not the logic for enabling accessibility specifically in the engraving module, but the logic for the entire application.
• If we need this value somewhere, we will either have to repeat this logic or ask the engraving, which will be strange.
• Now the engraving module depends on and knows about the navigation controller.

I propose to bring back iaccessibilitycontextconfiguration

[igorkorsukov]

I saw that this logic is duplicated in AccessibilityController, we can use it instead of iaccessibilitycontextconfiguration

[kryksyh]

I saw that this logic is duplicated in AccessibilityController, we can use it instead of iaccessibilitycontextconfiguration

Yes, you are right. My motivation to remove AccessibilyConfiguration was the fact that isAccessibleEnabled is not a configuration, but a current runtime state.
I replaced it with a call to AcecssibilityController