Proposal: Remove accessibility state 'disabled'

[CatchABus]

There is a case where this state causes conflict with isEnabled property when using Appium. See NativeScript/NativeScript#9455

Why having this state might be a bad idea? One of the reasons is that allowing developer to set this state to disabled but keep controls enabled may accidentally indicate discrimination to app users with disabilities.

I think UIAccessibilityTraitNotEnabled flag should be updated along with controls' `enabled' property as recommended.

myElement.isEnabled = true
myElement.accessibilityTraits &= ~UIAccessibilityTraitNotEnabled

myElement.isEnabled = false
myElement.accessibilityTraits |= UIAccessibilityTraitNotEnabled