For any enabled command, we should fire corresponding
beforeinput and input events.
Also update a WPT test to make it clearer what the
expected behavior is. None of the test expect a
beforeinput event. Before, it would fail with
"expected undefined, but got", which is not descriptive
as a failure to what's happening.
We are failing these tests, since this behavior is
currently unspecced and also requires changes in
the input element to work with text edits.
Part of #25005
Signed-off-by: Tim van der Lippe <tvanderlippe@gmail.com>