Bug 1830798 [wpt PR 39788] - Add popover hover triggering to buttons, a=testonly

Bug 1830798 [wpt PR 39788] - Add popover hover triggering to buttons, a=testonly

Automatic update from web-platform-tests
Add popover hover triggering to buttons

This is a semi-revert of [1], bringing back hover triggering for
popovers, including hints. Quite a few things have changed since [1]
landed, so this is mostly a re-implementation of hover triggering.
One big change is that hover triggering is only supported/possible on
a button element, rather than on any Element. This is to improve the
accessibility of this feature in case the user isn't using a mouse,
since the button will fall back to "regular" invoking behavior.

This capability is gated behind the HTMLPopoverHint feature.

[1] https://chromium-review.googlesource.com/c/chromium/src/+/3842343

Bug: 1416284
Change-Id: I8543c0a225b8cb085cc0d769b0fabb625cb9379c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4497330
Auto-Submit: Mason Freed <masonf@chromium.org>
Reviewed-by: Joey Arhar <jarhar@chromium.org>
Commit-Queue: Mason Freed <masonf@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1140440}

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wpt-commits: 8d8b273d2265095c7f5330ff231940e68fb49754
wpt-pr: 39788