Explicitly indicate when device clipboard is set

Pass the information that device clipboard has been set to the key
processor. This avoids the keyprocessor to "guess", and paves the way to
implement a proper acknowledgement mechanism.

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

app/src/trait/key_processor.h

@@ -18,8 +18,17 @@ struct sc_key_processor {
 };
 
 struct sc_key_processor_ops {
+
+    /**
+     * Process the keyboard event
+     *
+     * The flag `device_clipboard_set` indicates that the input manager sent a
+     * control message to synchronize the device clipboard as a result of this
+     * key event.
+     */
     void
-    (*process_key)(struct sc_key_processor *kp, const SDL_KeyboardEvent *event);
+    (*process_key)(struct sc_key_processor *kp, const SDL_KeyboardEvent *event,
+                   bool device_clipboard_set);
 
     void
     (*process_text)(struct sc_key_processor *kp,