Add --audio-buffer

Expose an option to add a buffering delay (in milliseconds) before
playing audio.

This is similar to the options --display-buffer and --v4l2-buffer for
video frames.

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

app/src/options.c

@@ -43,6 +43,7 @@ const struct scrcpy_options scrcpy_options_default = {
     .display_id = 0,
     .display_buffer = 0,
     .v4l2_buffer = 0,
+    .audio_buffer = 0,
 #ifdef HAVE_USB
     .otg = false,
 #endif