[AriaNotify] Add UseCounter

This CL adds a UseCounter for AriaNotify, which can be called via the
document or element. It also adds a wpt-internal test for the use counter.

More on AriaNotify in the explainer:
https://github.com/MicrosoftEdge/MSEdgeExplainers/blob/main/Accessibility/AriaNotify/explainer.md#screen-reader-customizations-for-user-preference

Bug: 326277796
Change-Id: Id190dbb6d3b136a900bd1e1f80db28fe8ea3545a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6374567
Reviewed-by: Alison Maher <almaher@microsoft.com>
Commit-Queue: Evelynn Kaplan <evelynn.kaplan@microsoft.com>
Cr-Commit-Position: refs/heads/main@{#1436357}