ipc: implement ext-data-control

wire/ext_data_control_manager_v1.txt

@@ -0,0 +1,14 @@
+# requests
+
+request create_data_source {
+    id: id(ext_data_control_source_v1),
+}
+
+request get_data_device {
+    id: id(ext_data_control_device_v1),
+    seat: id(wl_seat),
+}
+
+request destroy {
+
+}