Extension API fails to respect isEnabledForCluster

[Nokel81]

Because of the changes being made to ExtensionLoader the isEnabledForCluster() method on extensions is not being respected for most registrators. This means that even if that method is return false an extension's clusterPages, clusterPageMenus, etc... will still be shown.

Affects at least 5.5 and master, probably also some of 5.4.

Should not be referenced for the following (since these are only used in the root frame):

• entitySettings
• globalPages
• catalogEntityDetailItems
• appPreferences
• appPreferenceTabs
• statusBarItems
• commands (but should be called for commands in the cluster frame)
• welcomeMenus
• welcomeBanners
• topBarItems
• additionalCategoryColumns
• customCategoryViews

Should be references for the following:

• clusterPages Introduce kludge to make "isEnabledForCluster" work again for cluster pages PART 1 #5800
• clusterPageMenus Introduce kludge to make "isEnabledForCluster" work again for cluster page menus PART 2 #5801
• kubeObjectStatusTexts Introduce kludge to make "isEnabledForCluster" work again for kube object status texts PART 3 #5802
• kubeObjectDetailItems Introduce kludge to make "isEnabledForCluster" work again for kube object details PART 6 #5805
• kubeObjectMenuItems Introduce kludge to make "isEnabledForCluster" work again for kube object menu items PART 4 #5803
• kubeWorkloadsOverviewItems Introduce kludge to make "isEnabledForCluster" work again for workload overview details PART 5 #5804
• isEnabledForCluster is not respected for kubeObjectHandlers in Extension API #5830