Disable audio on initialization error

By default, audio is enabled (--no-audio must be explicitly passed to
disable it).

However, some devices may not support audio capture (typically devices
below Android 11, or Android 11 when the shell application is not
foreground on start).

In that case, make the server notify the client to dynamically disable
audio forwarding so that it does not wait indefinitely for an audio
stream.

Also disable audio on unknown codec or missing decoder on the
client-side, for the same reasons.

PR #3757 <https://github.com/Genymobile/scrcpy/pull/3757>

app/src/trait/packet_sink.h

@@ -23,6 +23,16 @@ struct sc_packet_sink_ops {
     bool (*open)(struct sc_packet_sink *sink, const AVCodec *codec);
     void (*close)(struct sc_packet_sink *sink);
     bool (*push)(struct sc_packet_sink *sink, const AVPacket *packet);
+
+    /*/
+     * Called when the input stream has been disabled at runtime.
+     *
+     * If it is called, then open(), close() and push() will never be called.
+     *
+     * It is useful to notify the recorder that the requested audio stream has
+     * finally been disabled because the device could not capture it.
+     */
+    void (*disable)(struct sc_packet_sink *sink);
 };
 
 #endif