rtsp: gstrtspurl: gst_rtsp_url_get_request_uri: use rtsps scheme for tls transport...

rtsp: gstrtspurl: gst_rtsp_url_get_request_uri: use rtsps scheme for tls transport methods

gst_rtsp_url_get_request_uri returns rtsp://... url when requested url is rtsps://, this is not
in accordance with https://www.rfc-editor.org/rfc/rfc7826.html#section-19.2.
This also impedes setting up a rtsps session with a live555 rtsp server.

Don't expose other than rtsp and rtsps internal gstreamer rtsp url schemes
to avoid regression:
https://gitlab.freedesktop.org/gstreamer/gstreamer/-/issues/2412

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/4298>