cleanup: Minimize deep_unpack() usage

deep_unpack()[1] will unpack a variant and its children, but only up to one level.
lookup_value()[2] will directly search for a value with a linear scan.

Performing a deep_unpack() + lookup can be a more expensive operation when we are
looking for just a single value compared to just perform the lookup_value() directly
in C. Avoid the deep_unpack() usage when we perform a single check presence.

[1] https://gjs.guide/guides/glib/gvariant.html#deepunpack
[2] https://docs.gtk.org/glib/method.Variant.lookup_value.html

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2416>

js/ui/status/nightLight.js

@@ -49,7 +49,8 @@ class Indicator extends SystemIndicator {
             g_interface_info: colorInfo,
         });
         this._proxy.connect('g-properties-changed', (p, properties) => {
-            if ('NightLightActive' in properties.deep_unpack())
+            const nightLightActiveChanged = !!properties.lookup_value('NightLightActive', null);
+            if (nightLightActiveChanged)
                 this._sync();
         });
         this._proxy.init_async(GLib.PRIORITY_DEFAULT, null)