tree: implement pointer constraints

wire/zwp_confined_pointer_v1.txt

@@ -0,0 +1,19 @@
+# requests
+
+msg destroy = 0 {
+
+}
+
+msg set_region = 1 {
+    region: id(wl_region),
+}
+
+# events
+
+msg confined = 0 {
+
+}
+
+msg unconfined = 1 {
+
+}