SECURITY: Ensure Message::rawParams can't lead to XSS

If you used wfMessage( 'foo' )->rawParams( 'bar"baz' )
there's a possibility of leading to xss, if the foo
message has a $1 in an attribute, as the quote characters
may end the attribute.

To prevent that, we convert $1 to $'"1 for after parameters,
so if any of them end up in attributes, the attribute escaping
will break the parameter name, preventing substitution.

This would of course break if someone intentionally inserted
a raw parameter into an attribute, but that's silly and I
don't think we should allow that.

This is similar to the parser strip marker issue.

Bug: T176247
Change-Id: If83aec01b20e414f9c92be894f145d7df2974866