Add sequence number to set_clipboard request

This will allow the client to request an acknowledgement.

PR #2814 <https://github.com/Genymobile/scrcpy/pull/2814>

app/src/control_msg.h

@@ -70,6 +70,7 @@ struct control_msg {
             // screen may only be turned on on ACTION_DOWN
         } back_or_screen_on;
         struct {
+            uint64_t sequence;
             char *text; // owned, to be freed by free()
             bool paste;
         } set_clipboard;