[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/firsttv.py

@@ -104,7 +104,7 @@ class FirstTVIE(InfoExtractor):
                     'tbr': tbr,
                     'source_preference': quality(f.get('name')),
                     # quality metadata of http formats may be incorrect
-                    'preference': -1,
+                    'preference': -10,
                 })
             # m3u8 URL format is reverse engineered from [1] (search for
             # master.m3u8). dashEdges (that is currently balancer-vod.1tv.ru)