utils: Shuffle and cleanup some paintable code

- It's only used in GcalShellSearchProvider so move it there.
- GdkTexture implements GIcon so no need to convert to a pixbuf.

src/utils/gcal-utils.c

@@ -183,49 +183,6 @@ get_circle_paintable_from_color (const GdkRGBA *color,
   return gtk_snapshot_to_paintable (snapshot, &GRAPHENE_SIZE_INIT (size, size));
 }
 
-/**
- * paintable_to_pixbuf:
- * @color: a #GdkRGBA
- * @size: the size of the surface
- *
- * Creates a circular surface filled with @color. The
- * surface is always @size x @size.
- *
- * Returns: (transfer full): a #cairo_surface_t
- */
-GdkPixbuf*
-paintable_to_pixbuf (GdkPaintable *paintable)
-{
-  g_autoptr (GtkSnapshot) snapshot = NULL;
-  g_autoptr (GskRenderNode) node = NULL;
-  g_autoptr (GskRenderer) renderer = NULL;
-  g_autoptr (GdkTexture) texture = NULL;
-  g_autoptr (GError) error = NULL;
-  graphene_rect_t viewport;
-
-  snapshot = gtk_snapshot_new ();
-  gdk_paintable_snapshot (paintable, snapshot,
-                          gdk_paintable_get_intrinsic_width (paintable),
-                          gdk_paintable_get_intrinsic_height (paintable));
-  node = gtk_snapshot_free_to_node (g_steal_pointer (&snapshot));
-
-  renderer = gsk_cairo_renderer_new ();
-  gsk_renderer_realize (renderer, NULL, &error);
-  if (error)
-    {
-      g_warning ("Couldn't realize Cairo renderer: %s", error->message);
-      return NULL;
-    }
-
-  viewport = GRAPHENE_RECT_INIT (0, 0,
-                                 gdk_paintable_get_intrinsic_width (paintable),
-                                 gdk_paintable_get_intrinsic_height (paintable));
-  texture = gsk_renderer_render_texture (renderer, node, &viewport);
-  gsk_renderer_unrealize (renderer);
-
-  return gdk_pixbuf_get_from_texture (texture);
-}
-
 /**
  * get_color_name_from_source:
  * @source: an #ESource

src/utils/gcal-utils.h

@@ -59,8 +59,6 @@ GdkPaintable*        gcal_get_paintable_from_color               (const GdkRGBA
 GdkPaintable*        get_circle_paintable_from_color             (const GdkRGBA      *color,
                                                                   gint                size);
 
-GdkPixbuf*           paintable_to_pixbuf                         (GdkPaintable       *paintable);
-
 void                 get_color_name_from_source                  (ESource            *source,
                                                                   GdkRGBA            *out_color);