Add --audio-codec=raw option

Add support for raw (PCM S16 LE) audio codec (a raw decoder is included
in FFmpeg).

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

app/src/server.c

@@ -173,6 +173,8 @@ sc_server_get_codec_name(enum sc_codec codec) {
             return "opus";
         case SC_CODEC_AAC:
             return "aac";
+        case SC_CODEC_RAW:
+            return "raw";
         default:
             return NULL;
     }