testsuite: Add a test for stripes

The GL renderer was creating sripes for nodes that were scaled in
particular ways, probably due to rounding errors.

This testsuite focuses on one of those stripes to make sure they are
gone.

testsuite/gsk/compare/texture-scale-stripes.node

@@ -0,0 +1,8 @@
+clip {
+  clip: 3950 3950 100 100;
+  child: texture-scale {
+    bounds: 0 0 19991 19991;
+    filter: nearest;
+    texture: url('data:,<svg><rect width="10" height="10" style="fill:red" /></svg>');
+  }
+}

testsuite/gsk/meson.build

@@ -77,6 +77,7 @@ compare_render_tests = [
   'scaled-texture',
   'shadow-in-opacity',
   'texture-scale-magnify-10000x',
+  'texture-scale-stripes',
   'texture-url',
   'transform-in-transform',
   'transform-in-transform-in-transform',