Bug 1860498 [wpt PR 42679] - Add invoketarget logic for popovers in button DefaultEve...

Bug 1860498 [wpt PR 42679] - Add invoketarget logic for popovers in button DefaultEventHandler, a=testonly

Automatic update from web-platform-tests
Add invoketarget logic for popovers in button DefaultEventHandler

This adds logic on how buttons with an invoketarget pointing to an
element with `popover` should behave, based on the Invokers proposal.

See explainer section here:
https://open-ui.org/components/invokers.explainer/#defaults.

See related spec PR here: https://github.com/whatwg/html/pull/9875

This introduces new behavior just within the HTML Form Control
`DefaultEventHandler` function such that:

 - If an `invoketarget` points to an element with `popover`
    - If the `invokeaction` is `auto` or `togglePopover`, try to toggle
      the popover
    - If the `invokeaction` is `hidePopover`, try to hide the popover
    - If the `invokeaction` is `showPopover`, try to show the popover

If the `invokeaction` is none of the above, then it will fall through
the to `HandleInvokeInternal` which is passed the lowercased atom so
element subclasses can handle their individual behaviors.

Bug: 1494737
Change-Id: Id2ab6faf8782a0fe0ba5c9f05ff562fee640f8b0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4964940
Reviewed-by: Joey Arhar <jarhar@chromium.org>
Reviewed-by: Mason Freed <masonf@chromium.org>
Commit-Queue: Luke <lukewarlow156@gmail.com>
Cr-Commit-Position: refs/heads/main@{#1215820}

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wpt-commits: a86d7454b3b6c8e33fed6a05b08ff081d62bf680
wpt-pr: 42679