iframe properties unreachable by abort-on-property-read/write snippets

Background

One of the CV provider use browser engine native functions like "attachShadow" from an iframe's window. With abort-on-property-read/write, we can only tackle the properties of the global window object. We need to find a way to tackle those properties that are not currently accessible.

What to change

I see 2 possible approaches:

• making 2 new snippets (eg. abort-on-iframe-property-read/write)
• add an option to existing snippets to support iframe properties also

Maybe we can discuss here and see the possible solutions to this.

/cc @hfiguiere @agiammarchi @skipintro @u.bernitt @amakram @a.omar