Fix a number of bugs in the ancestral popup algorithm

Prior to this change, there were several corner cases that would not
be properly handled, such as an anchor element that contains the
invoker of a lower-level popup. In addition, with this change, *any*
element that has an invoking attribute* that points to a popup, even
if it was not *used* to open that popup, will still act as an ancestral
popup relationship, and will not cause that popup to be light dismissed
if clicked.

See:
  openui/open-ui#508

* `togglepopup` for now, soon to also be `showpopup` and `hidepopup`

Bug: 1307772
Change-Id: I443ffd1884abfdb2856dc5d946323de4b83e20e4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3601261
Auto-Submit: Mason Freed <masonf@chromium.org>
Reviewed-by: Dan Clark <daniec@microsoft.com>
Commit-Queue: Mason Freed <masonf@chromium.org>
Cr-Commit-Position: refs/heads/main@{#995882}