Improve global notification settings

Separate the setting for globally setting push rules on/off from the configuration to decide whether desktop popup notifications are sent.

The current master setting is pulling double duty and should probably be separate as some people may want to see notification counts in Neochat but don't want to see popup notifications on their desktop.

src/qml/Settings/GlobalNotificationsPage.qml

@@ -19,14 +19,12 @@ Kirigami.ScrollablePage {
 
         MobileForm.FormCard {
             Layout.fillWidth: true
-
             contentItem: MobileForm.FormCheckDelegate {
                 text: i18n("Enable notifications for this account")
-                checked: Config.showNotifications
-                enabled: !Config.isShowNotificationsImmutable && Controller.activeConnection
+                description: i18n("Whether push notifications are generated by your Matrix server")
+                checked: NotificationsManager.globalNotificationsEnabled
+                enabled: NotificationsManager.globalNotificationsSet
                 onToggled: {
-                    Config.showNotifications = checked
-                    Config.save()
                     NotificationsManager.globalNotificationsEnabled = checked
                 }
             }