Add support for custom accessibility actions

[ihor-kravchenko-evinced]

Summary

This PR introduces support for exposing accessibility custom actions as an element attribute using private XCTest APIs.

Motivation

Once this is in place:

• Custom actions become visible in the element tree.
• Clients like Appium (or other accessibility tools) can read them and make further validations or conclusions.
• Accessibility regressions related to custom actions become detectable.

Implementation Notes

• The value is retrieved using private attribute _XC_kAXXCAttributeCustomActions

These changes are additive, so they do not change existing behaviour.

[linux-foundation-easycla]

• ❌ - login: @igorkravchenko / name: Igor Kravchenko . The commit (6fbf62e, ef710c2, f75e067) is not authorized under a signed CLA. Please click here to be authorized. For further assistance with EasyCLA, please submit a support request ticket.

[mykola-mokhnach]

The PR looks ok

Please also add some integration tests to cover the new functionality for page source generation and element attributes fetching. Also, do not forget to update the element double declaration in unit tests

[KazuCocoa]

Do we need a space after ,? If not, then it makese sense to use only , to not add redundant spaces in WDA layer

[ihor-kravchenko-evinced]

@KazuCocoa Thank you for pointing it out. I wonder if comma delimiter is reliable at all since action titles can contain commas themselves so consumers can’t reliably split.

[KazuCocoa]

I meant a space after , like below was needed here:

ah, you meant conman itself also. Agree with that, but I have no much good idea another word though