gsturi: Add new API for storing unmodified userinfo / fragment

gsturi: Add new API for storing unmodified userinfo / fragment

New API: gst_uri_from_string_escaped()

Identical to gst_uri_from_string() except that the userinfo and
fragment components of the URI will not be unescaped while parsing.

This is needed for correctly parsing usernames or passwords with `:`
in them such as reported at:
https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/issues/831

Change-Id: Ib46abff5f24e259a5e505092fcc99b3fdc82ca3e
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/583>