testsuite: Add a compare test for non-integer repeat children

This encodes the problems from the harmless looking example from
  https://blog.gtk.org/2024/01/28/new-renderers-for-gtk/
in a form that we can test.

Unsurprisingly it doesn't work on GL and Cairo.

testsuite/gsk/compare/repeat-noninteger-nogl-nocairo.node

@@ -0,0 +1,13 @@
+/* Repeat a child node that is not an integer size
+   and check that there's no space between the
+   tiles.
+   A color node is the easiest way to do that without
+   having to deal with visual glitches.
+ */
+repeat {
+  bounds: 0 0 50 50;
+  child: color {
+    bounds: 0 0 0.5 0.5;
+    color: rgb(255,0,0);
+  }
+}

testsuite/gsk/meson.build

@@ -122,6 +122,7 @@ compare_render_tests = [
   'repeat-no-repeat',
   'repeat-node-tiling-horizontal',
   'repeat-node-tiling-vertical',
+  'repeat-noninteger-nogl-nocairo',
   'repeat-repeats',
   'repeat-repeats-nested-nogl',
   'repeat-scaling',