vo: move libmpv back to the bottom in the auto-probing order

[Akemi]

this basically reverts commit 7b5a258. this was done for macOS since the only working vo was cocoa-cb (libmpv) and it would otherwise always use the deprecated opengl cocoa backend.

we now have a working vulkan gpu/gpu-next backend on macOS which should be the new default vo. vo=libmpv has to be explicitly set now to use cocoa-cb.

@Dudemanguy @jeeb

i am not sure if it's a problem that libmpv won't be used as a fallback like this and vo=libmpv has to be explicitly set to use it? we will probably get a few issues in the future when mpv is not build with vulkan support and without moltenvk, since it won't playback anything even if cocoa-cb is included in the build. also should this probing check be reverted too, i am not sure what exactly it is for? https://github.com/mpv-player/mpv/commit/7b5a2588bd33d5cf532a1c83d79dba20a3f26bc5#diff-f7289f81cef5c1b17fc94b82798c1364fa3eff40bbcab6776611e892880cf7d1L557-R558

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• mpv-i686-w64-mingw32
• mpv-x86_64-w64-mingw32

[Dudemanguy]

also should this probing check be reverted too

We could let libmpv be probed on macos but not any other OS.

[Akemi]

We could let libmpv be probed on macos but not any other OS.

if this isn't a too big change it is probably worthwhile, since it might keep a lot of unnecessary issues away from us. though i have no idea how to do that, since i have no clue about that part of the code.

[Dudemanguy]

If you just move &video_out_libmpv above &video_out_null, so it can be autoprobed. And then in vo_libmpv itself something like:

#if !HAVE_DARWIN
    if (vo->probing)
        return -1;
#endif

Or whatever define is more appropriate.

[Akemi]

thanks, now this part of the code makes a lot more sense to me. i guarded the the check behind HAVE_MACOS_COCOA_CB, since it's only really relevant when mpv is built with cocoa-cb support. if we ever remove vo=libmpv this can be removed completely.

i also updated the commit message and the note in api changes to properly reflect the change in behaviour now. if you are fine with the changes feel free to merge it or just let me know and i will do it.

[Dudemanguy]

LGTM, feel free to merge whenever.