options: restore old default sub selection behavior

1669c4698d notably flipped the default of
--subs-with-matching-audio from yes to no as part of a series of changes
that gave more control over sub selection behavior. While the increased
amount of options is definitely nice, changing the default to no results
in very unintuitive behavior. For example, setting alang=en and slang=en
in your config will not show any subtitles since the audio stream is
English as well so --subs-with-matching-audio being no causes the subs
to not be be selected. This is very weird for users who reasonably
expect slang being set to actually result in showing subs and this is
what mpv did for the past decade.

The other case is when a subtitle does not have a language tag but is
flagged as default. Because --subs-fallback (a new option), defaults to
no, these subtitles also will not be loaded. This is also strange for
users since mpv previously loaded these and they would need to change
the value of this option. It's also inconsistent because audio tracks
that are tagged as default are also loaded by default.

The new behavior seems to have mostly just confused users, and it also
regresses their configs for unclear reasons. Let's just set the options
to be back in line with the old behavior with is what most users expect.
--subs-with-matching-audio goes back to being yes and the new option
--subs-fallback should be default. Fixes #11854.

DOCS/interface-changes.rst

@@ -29,6 +29,8 @@ Interface changes
  --- mpv 0.37.0 ---
     - `--save-position-on-quit` and its associated commands now store state files
       in %LOCALAPPDATA% instead of %APPDATA% directory by default on Windows.
+    - change `--subs-with-matching-audio` default from `no` to `yes`
+    - change `--subs-fallback` default from `no` to `default`
  --- mpv 0.36.0 ---
     - add `--target-contrast`
     - Target luminance value is now also applied when ICC profile is used.

DOCS/man/options.rst

@@ -140,11 +140,11 @@ Track Selection
 
 ``--subs-with-matching-audio=<yes|no>``
     When autoselecting a subtitle track, select a full/non-forced one even if the selected
-    audio stream matches your preferred subtitle language (default: no).
+    audio stream matches your preferred subtitle language (default: yes).
 
 ``--subs-fallback=<yes|default|no>``
     When autoselecting a subtitle track, if no tracks match your preferred languages,
-    select a full track even if it doesn't match your preferred subtitle language (default: no).
+    select a full track even if it doesn't match your preferred subtitle language (default: default).
     Setting this to `default` means that only streams flagged as `default` will be selected.
 
 ``--subs-fallback-forced=<yes|no>``

options/options.c

@@ -1040,7 +1040,8 @@ static const struct MPOpts mp_default_opts = {
         [STREAM_SUB] = (char *[]){ "auto", NULL },
     },
     .stream_auto_sel = true,
-    .subs_with_matching_audio = false,
+    .subs_with_matching_audio = true,
+    .subs_fallback = 1,
     .subs_fallback_forced = true,
     .audio_display = 1,
     .audio_output_format = 0,  // AF_FORMAT_UNKNOWN