[ACT:6a7281]: Separate required and supported aria states and properties

[shunguoy]

Aria required and supported states and properties may need to be handled differently when checking the values. For example, based on the ACT test case description:

Only for WAI-ARIA required properties with value types ID Reference and ID Reference List is there a requirement that the elements with the given ids actually exist. For non-required properties, this is not a requirement. For example, the value of the aria-errormessage attribute on input does not need to reference an id that exists within the same document, because an HTML element with such an id may be created in response to an event that may or may not happen.

The ACT passed example 4: <div role="textbox" aria-errormessage="my-error" aria-label="A textbox"></div>

The engine currently reports a violation for the case:

[MHoov]

Currently this is a proposed rule

[philljenkins]

The ACT test case has changed, and now Passed Example 5: https://www.w3.org/WAI/content-assets/wcag-act-rules/testcases/6a7281/e4b47e094d44a9f3b5b3fd5c157f3ef6679bede0.html