testsuite: Add test cases for last commit

Easy enough to test

testsuite/gsk/compare/transform-in-transform-in-transform.node

@@ -0,0 +1,14 @@
+transform {
+  child: transform {
+    child: transform {
+      child: color {
+        bounds: 0 0 20 20;
+        color: blue;
+      }
+      transform: translate(0, -20);
+    }
+    transform: rotate(90);
+  }
+
+  transform: translate(300, 200);
+}

testsuite/gsk/compare/transform-in-transform.node

@@ -0,0 +1,10 @@
+transform {
+  child: transform {
+    child: color {
+      bounds: 0 0 20 20;
+      color: blue;
+    }
+    transform: translate(0, -20);
+  }
+  transform: scale(2) rotate(90);
+}

testsuite/gsk/meson.build

@@ -64,6 +64,8 @@ compare_render_tests = [
   'inset-shadow-multiple',
   'borders-rotated',
   'blend-invisible-child',
+  'transform-in-transform',
+  'transform-in-transform-in-transform',
 ]
 
 # these are too sensitive to differences in the renderers