LibWeb: Add Location.ancestorOrigins

[Psychpsyo]

Implements the ancestorOrigins property on Location objects.
Not 100% sure how to properly test this and there's no WPT coverage either, but the feature might also still get changed, as per the spec comment.

[shannonbooth]

I am not sure we should implement this, gecko does not implement this due to privacy concerns (so my opinion is we probably should not). From what I understand this is really only used by ad-tech out on real sites.

[tcl3]

FWIW, there was some previous discussion on #623 about how to implement this API in a way that preserves user privacy.

[Psychpsyo]

I am not sure we should implement this, gecko does not implement this due to privacy concerns (so my opinion is we probably should not). From what I understand this is really only used by ad-tech out on real sites.

That makes sense, since I saw the error pop up on Youtube.
I'll convert this to a draft until that gets resolved then since I don't personally care much about this property myself.

[shannonbooth]

It may be worth changing the IDL to not have [FIXME] in it, and instead leave a comment saying that we have chosen not to implement and are waiting for when/if the spec changes to address those concerns