compiletest: normalization replacement strings don't support newlines

[jieyouxu]

It will affect every normalize- header, but since none of those currently have a \n in them, no other tests will be affected (other than the one I'm adding).

There is currently no way to a new-line in the replacement string, I tried a bunch of things and just gave up and added this mini logic.

Originally posted by @Urgau in #133710 (comment)