Remove ExtenedMap, ToggleSet, and observable versions (#3310)

- Switch to helper functions instead. They don't impact the prototype
  tree and it means that we don't need to introduce versions that are
  both observable and "normal"

- Tidy <ItemListLayout> and hiddenTableColumns to not need
  pre-initialization

Signed-off-by: Sebastian Malton <sebastian@malton.name>

src/renderer/components/+config-secrets/secret-details.tsx

@@ -27,7 +27,7 @@ interface Props extends KubeObjectDetailsProps<Secret> {
 export class SecretDetails extends React.Component<Props> {
   @observable isSaving = false;
   @observable data: { [name: string]: string } = {};
-  revealSecret = new Set<string>();
+  @observable revealSecret = observable.set<string>();
 
   constructor(props: Props) {
     super(props);