SettingsWindow Loading

- reworked the way we load the settings to avoid using
Qt.createComponent which breaks hot reload and more
- introduced a new PanelManager singleton to hold some references to
some panels and later will be used to force having a single panel opened
at all time

Services/PanelManager.qml

@@ -0,0 +1,10 @@
+pragma Singleton
+
+import Quickshell
+import qs.Modules.Settings
+
+Singleton {
+  id: root
+
+  property SettingsWindow settingsWindow: null
+}