(core) Rename popup for group by columns

Summary:
Showing rename popup on group by column with disabled label section. It only allows to set description.

Unrelated:
- Fixing HostedMetadataManager test

Test Plan: Updated tests

Reviewers: Spoffy

Reviewed By: Spoffy

Subscribers: Spoffy

Differential Revision: https://phab.getgrist.com/D4371

app/common/gutil.ts

@@ -999,7 +999,11 @@ export function useBindable<T>(use: UseCBOwner, obs: BindableValue<T>): T {
 /**
  * Useful helper for simple boolean negation.
  */
-export const not = (obs: Observable<any>|IKnockoutReadObservable<any>) => (use: UseCBOwner) => !use(obs);
+export const not = (obs: Observable<any>|IKnockoutReadObservable<any>|boolean|undefined|null) => (use: UseCBOwner) =>  {
+  if (typeof obs === 'boolean') { return !obs; }
+  if (obs === null || obs === undefined) { return true; }
+  return !use(obs);
+};
 
 /**
  * Get a set of up to `count` distinct values of `values`.