tests: Always use the bundled cursor theme

To not depend on the system cursor theme for tests, always use
our own, even if the cursor theme appearance makes no difference.
We also need to add all of Adwaita's cursors in tree, to avoid any test
arbitrarily triggering missing cursor warnings or errors.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/4307>

src/tests/cursor-tests.c

@@ -672,7 +672,6 @@ main (int    argc,
       char **argv)
 {
   g_autoptr (MetaContext) context = NULL;
-  g_autofree char *path = NULL;
 
   context = meta_create_test_context (META_CONTEXT_TEST_TYPE_TEST,
                                       (META_CONTEXT_TEST_FLAG_NO_X11 |
@@ -682,9 +681,6 @@ main (int    argc,
   meta_context_test_set_background_color (META_CONTEXT_TEST (context),
                                           COGL_COLOR_INIT (255, 255, 255, 255));
 
-  path = g_test_build_filename (G_TEST_DIST, "tests", "xcursors", NULL);
-  g_setenv ("XCURSOR_PATH", path, TRUE);
-
   test_context = context;
 
   init_tests ();

src/tests/meta-context-test.c

@@ -82,6 +82,15 @@ ensure_gsettings_memory_backend (void)
                  G_TYPE_FROM_INSTANCE (default_backend));
 }
 
+static void
+ensure_xcursor_path (void)
+{
+  g_autofree char *xcursor_path = NULL;
+
+  xcursor_path = g_test_build_filename (G_TEST_DIST, "xcursors", NULL);
+  g_setenv ("XCURSOR_PATH", xcursor_path, TRUE);
+}
+
 static void
 meta_context_test_finalize (GObject *object)
 {
@@ -125,6 +134,7 @@ meta_context_test_configure (MetaContext   *context,
   meta_context_set_plugin_gtype (context, META_TYPE_TEST_SHELL);
 
   ensure_gsettings_memory_backend ();
+  ensure_xcursor_path ();
 
   return TRUE;
 }