feat: Add isAccessible field into element page source representation

[TheDarkestDay]

This is the follow-up PR for discussion raised here - appium/appium#15232.

In our use case we would like to run several accessibility checks, relying on the information provided by page source. However, it is difficult to distinguish which elements should be accessible or not (and therefore, should be checked against accessibility checks) without actually having this information inside the tree.

WebDriver allows to grab isAccessible field for individual element, on the other hand requesting this data for each element takes immense amount of time.

That's why we think that it would be great to expose this field via page source sent by /source endpoint. This is the whole purpose of this PR.

Feel free to express any thoughts or concerns.

[mykola-mokhnach]

The PR only adds this attribute to the JSON representation of the page tree. XML tree will remain unchanged. Is such behaviour expected?

[TheDarkestDay]

The PR only adds this attribute to the JSON representation of the page tree. XML tree will remain unchanged. Is such behaviour expected?

No, I think this is my bad. I guess it should be available in general, without any dependency on data representation type.

[mykola-mokhnach]

Some tests are still failing. Please update them. Regarding the changes in the code: LGTM

[TheDarkestDay]

I am afraid I am a little bit stuck at this point. There is a job which failed with some compilation error https://dev.azure.com/AppiumCI/Appium%20CI/_build/results?buildId=14928&view=logs&j=e09f1c88-ad07-58cd-1353-eec10b5bcfad&t=f942f577-1cf3-5a58-01a8-f7ff19fbb293&l=59. Neither can I really understand what causes it nor I can get the same error locally.

Have you ever experienced something like this? Does it make any sense to try re-running this job? Or am I missing something in my changes? Sorry for this.

[mykola-mokhnach]

To me it looks like a CI glitch, which is not related to the original PR changes.