UI: Enable multiple audio tracks in Simple Output recording

This adds support for multiple audio tracks in Simple Output for
recordings.
This is enabled for all quality presets (including "Lossless") except
"Same as Stream".
This is also enabled for the Replay Buffer.
An exception is made for flv recording format since it only allows a
single audio track.
The recorded track (and streaming track) is then Track 1 as before.

Signed-off-by: pkv <pkv@obsproject.com>

UI/window-basic-main.cpp

@@ -1534,6 +1534,8 @@ bool OBSBasic::InitBasicConfigDefaults()
 				  "StreamAudioEncoder", "aac");
 	config_set_default_string(basicConfig, "SimpleOutput",
 				  "RecAudioEncoder", "aac");
+	config_set_default_uint(basicConfig, "SimpleOutput", "RecTracks",
+				(1 << 0));
 
 	config_set_default_bool(basicConfig, "AdvOut", "ApplyServiceSettings",
 				true);