Update Core-AAM aria-errormessage to take multiple element references

[cyns]

Align Core-AAM with ARIA PR 1802 issue 1730
change aria-errormessage to take multiple element references

IA2 and ATK/AT-SPI already point to multiple nodes
update UIA to have ControllerFor point to an array of references to accessibility nodes

@cookiecrook need text for AX API. Assign back to me with text
Old text is
AX API | Property: AXValidationError: textual content of the referenced element

[mrego]

BTW, it looks like WebKit code is using AXErrorMessageElements for this: https://github.com/WebKit/WebKit/blob/597d9d53ad4bc9ccc50eb87259778167ecf69329/Source/WebCore/accessibility/mac/WebAccessibilityObjectWrapperMac.mm#L2636

[sivakusayan]

Just a heads up, I'm updating Blink's aria-errormessage to take in multiple element references and was planning on copying what WebKit was doing (so just exposing aria-errormessage through AXErrorMessageElements on macOS).