Subsurface order isn't respected on mouse click and causes issue for Firefox

[lilydjwg]

Describe the bug

When a right click happens on a popup of Firefox, Firefox may create subsurfaces that are intended to be above the popup itself, but since the click happens on the popup, the popup is brought to front instead.

Click on an invalid menuitem on the should-be-topmost subsurface will bring it up, if it is possible.

This may also be the issue that sometimes the tab preview (when hovering on a tab) doesn't show up.

To Reproduce
Please see https://bugzilla.mozilla.org/show_bug.cgi?id=1943240.

Expected behavior
A clear and concise description of what you expected to happen.

Screenshots or stacktrace

Wayfire version
git.