tests: Add rudimentary color device test

Tests that test case EDID is setup correctly, and that color devices for
monitors are created.

tests/color: Add hotplugging tests

Checks that changing the number of connected monitors reflects the
number of current color devices, and that we end up with the correct end
state.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2164>

src/tests/meta-monitor-test-utils.c

@@ -768,6 +768,15 @@ meta_create_monitor_test_setup (MetaBackend          *backend,
       output_info->tile_info = setup->outputs[i].tile_info;
       output_info->panel_orientation_transform =
         setup->outputs[i].panel_orientation_transform;
+      if (setup->outputs[i].has_edid_info)
+        {
+          output_info->edid_info = g_memdup2 (&setup->outputs[i].edid_info,
+                                              sizeof (setup->outputs[i].edid_info));
+          output_info->edid_checksum_md5 =
+            g_compute_checksum_for_data (G_CHECKSUM_MD5,
+                                         (uint8_t *) &setup->outputs[i].edid_info,
+                                         sizeof (setup->outputs[i].edid_info));
+        }
 
       output = g_object_new (META_TYPE_OUTPUT_TEST,
                              "id", (uint64_t) i,