[formatsort] Remove misuse of 'preference'

'preference' is to be used only when the format is better that ALL qualities of a lower preference irrespective of ANY sorting order the user requests. See deezer.py for correct use of this

In the older sorting method, `preference`, `quality` and `language_preference` were functionally almost equivalent. So these disparities doesn't really matter there

Also, despite what the documentation says, the default for `preference` was actually 0 and not -1. I have tried to correct this and also account for it when converting `preference` to `quality`

youtube_dlc/extractor/iqiyi.py

@@ -373,7 +373,7 @@ class IqiyiIE(InfoExtractor):
                     'url': stream['m3utx'],
                     'format_id': vd,
                     'ext': 'mp4',
-                    'preference': self._FORMATS_MAP.get(vd, -1),
+                    'quality': self._FORMATS_MAP.get(vd, -1),
                     'protocol': 'm3u8_native',
                 })