User can browse and select from available generators in interactive manner

When building or editing a Medusa Dataset file, users need visibility into the available generators and the arguments they require. To support this, a CodeLens option should be added to Dataset files that enables browsing and selecting generators for each field.

Proposed behavior:

**Browse Generators**
- Invoke the `GET /v1/generators `Medusa endpoint.
- Display generator names, descriptions, and argument details.

**Select Generator**
- When a generator is selected, insert the generator structure into the Dataset file at the target field.