This begins implementation on form-associated custom elements.
This fixes a few WPT tests which I'm importing.
Co-authored-by: Sam Atkins <sam@ladybird.org>
Previously, a crash would occur when attempting to throw an error in
this case because the method used to create the exception tried to get
the current realm from the execution context stack, which is empty. The
realm is now passed explicitly when constructing the error, avoiding
the crash.