Fixed #19508 -- Used uri_to_iri.

This is a PR for ticket #19508 for which another PR #2919 was opened by me a few days ago.
This PR implements `uri_to_iri` as per RFC and changes the `PATH_INFO` at the very time when `environ` is being set contrary to the previous one which corrected the received url from `environ`.
I have put the if statement so that answer can be obtained in bytes as well by passing None in that kwarg.

`repercent_broken_unicode` does not works on latin-1 strings, that is done after.