Add a means by which UIA clients can determine whether a build of Windows Terminal does or doesn't support notifications

Description of the new feature/enhancement

#12358 adds support for UIA notifications, allowing screen readers and other UIA clients to easily determine exactly what new text to report without doing any of the heavy lifting themselves (diffing, etc..). However, as not all terminals support notifications, UIA clients need a way to determine when this support is available and when they should fall back to performing diffing themseles. (if clients diff even when notifications are available, we risk doing extra work and/or double-reporting incoming text).

Proposed technical implementation details (optional)

• In #12358 and over email at various times, we discussed using a different class name (TermCtrl2) for situations when notifications are available. NVDA supports this new ID today, but there were concerns from JAWS.
• We also discussed sending an "API version" of sorts through a custom property. This is necessary since wt and conhost versions aren't necessarily tied to particular Windows releases/aren't reliable for feature detection.