testsuite: Add a test for a recent mipmap generation bug

Tests the fix in ab1fba6fdc.

Related: #6298
Related: !6704

testsuite/gsk/compare/mipmap-generation-later.node

@@ -0,0 +1,13 @@
+texture-scale {
+  bounds: 0 0 10 10;
+  filter: nearest;
+  texture: "texture1" url("data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACgAAAAoCAYAAACM/rhtAAAAZklEQVRYhe3SoQ3AMBAEwXOUQtJ/\
+Ve7kAxJqtOTADrGOWa9dszN58tn/W7TXJNPwkdO+Uu7OTsWlTrv+gjZI2SBlg5QNUjZI2SBlg5QN\
+UjZI2SBlg5QNUjZI2SBlg5QNUjZI1Tf4AnlN8eRDOVeLAAAAAElFTkSuQmCC\
+");
+}
+texture-scale {
+  bounds: 15 0 10 10;
+  filter: trilinear;
+  texture: "texture1";
+}

testsuite/gsk/meson.build

@@ -85,6 +85,7 @@ compare_render_tests = [
   'mask-modes-in-opacity',
   'mask-modes-with-alpha',
   'mask-texture-color-alpha',
+  'mipmap-generation-later',
   'nested-rounded-clips',
   'offscreen-pixel-alignment-nogl-nocairo',
   'opacity_clip',