[Improvement] Gravitinoi UI can create new metalakes but not effectively use them in playground

### What would you like to be improved?

The Gravitino playground is configured to use simple names but the UI enables you to create new metalakes.

### How should we improve?

Stop UI from being able to create new metalakes when using simple names?

Start in the Gravitino playground UI where metalake creation is exposed, and inspect how the simple-name configuration is represented. Done means the UI no longer allows creating new metalakes when the playground uses simple names, while the existing playground behavior remains usable.

Written by the indexing model from the issue text.