Convert to using list of accessibility elements for iOS tab indexes

[PureWeen]

Description of Change

Convert to using list of accessibility elements over methods. My theory here is that the performance of the individual methods when going across the bridge was causing hiccups with Appium.

I noticed on a ListView that it would call the "getMethods" for every single elements as you moved the mouse around which caused it to move incredibly slow.

Once I swapped over to just using the getter it all seemed to work much smoother

#9702 (comment)

Issues Resolved

• fixes [Bug] Appium and Xamarin Forms 4.0 Compatibility (iOS) #6667
• fixes [Bug] Appium tests (iOS). UI elements are missing from page source XML representation with Xamarin 4.6 update #11026

Platforms Affected

• iOS

Testing Procedure

• @samhouts

PR Checklist

• Targets the correct branch
• Tests are passing (or failures are unrelated)

[PureWeen]

The documentation for this property says the default is null
https://developer.apple.com/documentation/objectivec/nsobject/1615147-accessibilityelements

Containers can implement this property instead of the dynamic methods to support the retrieval of the contained elements. The default value of this property is nil.

When I do that it seems like the accessibility just returns to the default behavior. I added all the repro's from the PR listed here #9702 and I tested the Accessibility demo on xamarin-samples.

We might need to add the setAccessibilityElements side of this as well for certain edge cases.

For now we'll keep it simple and see if that works

[PureWeen]

Failures unrelated

[PureWeen]

@arevellfraedom summarized these properties really well here #9702 (comment)

@arevellfraedom I've tested through all the issues associated with issue #9702 and added UI Tests for them as well

If you have any additional cases or things you feel this PR might break please let me know

AFAICT this statement you made

I think sending null might even remove an override, but haven't checked.

Is true

Here's the nuget if you want to test
https://dev.azure.com/xamarin/public/_build/results?buildId=21211&view=artifacts&type=publishedArtifacts

[PureWeen]

All green

[samhouts]

Wunderbar!