(Replaces #177195, which was about just one setting. This issue covers the whole bundle of related settings.)

Use case

In the Zulip app for iOS, we'd like to check whether the iOS 17+ "Auto-Play Animated Images" setting is enabled, so that when loading an image, we can choose between animated and still versions.

• iOS user doc: https://support.apple.com/guide/iphone/reduce-onscreen-motion-iph0b691d3ed/ios
• iOS developer doc: https://developer.apple.com/documentation/swiftui/environmentvalues/accessibilityplayanimatedimages

Proposal

I propose adding new fields to AccessibilityFeatures, providing "Auto-Play Animated Images" and, for completeness, all the related settings in that Apple user doc:

• Reduce Motion (already exposed, as AccessibilityFeatures.reduceMotion)
• Vehicle Motion Cues
• Dim Flashing Lights
• Auto-Play Animated Images (for Zulip's use case; was tracked in Expose iOS "Auto-Play Animated Images" accessibility setting #177195)
• Auto-Play Video Previews
• Auto-Play Message Effects
• Prefer Non-Blinking Cursor
• Limit Frame Rate

We would follow the existing pattern of iOS-only fields, such as AccessibilityFeatures.onOffSwitchLabels, by saying in the dartdocs "Only supported on iOS."