ytdl_hook: use tbr for all tracks if vbr/abr not available

vbr and abr are the video and audio bitrates. Sometimes there is a weird
mix of any of them available, but in these cases, it's not good to fall
back to tbr if a specific track has no vbr/abr.

For example, the alphabetic site provides tbr only for the muxed
fallback stream, but using tbr would make the primitive mpv hls_bitrate
selection pick the compatibility stream for audio, because it appears to
have a higher bitrate than the other audio-only streams (because the
bitrate includes video). So we must not use tbr in this case.

On the other hand, formats coming from youtube-dl HLS master playlist
use will only have tbr set.

So as a heuristic, use the tbr only if it's the only bitrate available
in any track entry.

player/lua/ytdl_hook.lua

@@ -344,6 +344,12 @@ local function formats_to_edl(json, formats, use_all_formats)
     local single_url = nil
     local streams = {}
 
+    local tbr_only = true
+    for index, track in ipairs(formats) do
+        tbr_only = tbr_only and track["tbr"] and
+                   (not track["abr"]) and (not track["vbr"])
+    end
+
     for index, track in ipairs(formats) do
         local edl_track = nil
         edl_track = edl_track_joined(track.fragments,
@@ -392,6 +398,9 @@ local function formats_to_edl(json, formats, use_all_formats)
                 if #tracks > 1 then
                     rates = {({video = "vbr", audio = "abr"})[sub.media_type]}
                 end
+                if tbr_only then
+                    rates = {"tbr"}
+                end
                 for _, f in ipairs(rates) do
                     local br = as_integer(track[f])
                     if br > 0 then