loadfile: improve the format of terminal track information

Print vlang if present.

Make unselected tracks and editions grey instead of adding (+) before
selected tracks. Mark them with the same circles as show-text
${track-list} and script-message osc-tracklist when not outputting to a
TTY.

Don't print a different symbol with --sub-forced-events-only because
nobody uses this option, and subtitles are very unlikely to mix forced
and non-forced events.

Align 2-digit track IDs.

Align languages of up to 7 characters (the length of zh-Hans).

Leave spaces when a track has no language but at least another track
does to align the following track data with the other tracks.

Add a space between values and their units.

Convert Hz to kHz.

Pretty print FPS and kHz with mp_format_double().

Don't print images' FPS because it's just a bogus value taken from
--mf-fps.

Co-authored-by: Kacper Michajłow <kasper93@gmail.com>

osdep/terminal.h

@@ -38,6 +38,8 @@
 #define TERM_ESC_ENABLE_MOUSE       "\033[?1003h"
 #define TERM_ESC_DISABLE_MOUSE      "\033[?1003l"
 
+#define TERM_ESC_GREY               "\033[38;5;8m"
+
 struct input_ctx;
 
 /* Global initialization for terminal output. */