Add option to select video codec

Introduce the selection mechanism. Alternative codecs will be added in
further commits.

PR #3713 <https://github.com/Genymobile/scrcpy/pull/3713>

app/src/scrcpy.c

@@ -315,6 +315,7 @@ scrcpy(struct scrcpy_options *options) {
         .select_usb = options->select_usb,
         .select_tcpip = options->select_tcpip,
         .log_level = options->log_level,
+        .codec = options->codec,
         .crop = options->crop,
         .port_range = options->port_range,
         .tunnel_host = options->tunnel_host,