osc.lua: remove NIH list formatting

All of the code to format playlist/track-list/chapter-list is
unnecessary when mpv's core can already show-text these properties.

Also an issue with this custom formatting is that showing fewer entries
than can fit on the OSD can make it seem like the playlist ends there
and there are no entries afterwards.

Also remove lots of pointless code around the track-list (mpv's track id
and the osc_id are exactly the same).

This simplification will make it easier to bind customizable commands,
otherwise yet another script message to call set_track would have to be
added, when cycle sub/audio already output information about the new
track on their own.

DOCS/man/osc.rst

@@ -493,10 +493,6 @@ Script Commands
 The OSC script listens to certain script commands. These commands can bound
 in ``input.conf``, or sent by other scripts.
 
-``osc-message``
-    Show a message on screen using the OSC. First argument is the message,
-    second the duration in seconds.
-
 ``osc-visibility``
     Controls visibility mode ``never`` / ``auto`` (on mouse move) / ``always``
     and also ``cycle`` to cycle between the modes.
@@ -515,8 +511,3 @@ to set auto mode (the default) with ``b``::
 ``osc-idlescreen``
     Controls the visibility of the mpv logo on idle. Valid arguments are ``yes``,
     ``no``, and ``cycle`` to toggle between yes and no.
-
-``osc-playlist``, ``osc-chapterlist``, ``osc-tracklist``
-    Shows a limited view of the respective type of list using the OSC. First
-    argument is duration in seconds.
-