Add option --max-fps

Add an option to limit the capture frame rate. It only works for devices
with Android >= 10.

Fixes <https://github.com/Genymobile/scrcpy/issues/488>

app/src/server.h

@@ -35,6 +35,7 @@ struct server_params {
     uint16_t local_port;
     uint16_t max_size;
     uint32_t bit_rate;
+    uint16_t max_fps;
     bool control;
 };