[FEATURE] Support `testConnection` Without Catalog Name in Gravitino

### Describe the feature

### Description:
The `testConnection` method currently requires a catalog name, as it depends on Metalake, which enforces this. However, there are cases where we need to validate the connection using only `provider` and `properties` before creating a catalog. This limitation makes it difficult to test connections early in the workflow.

### Motivation

- Enables connection testing before catalog creation.
- Simplifies workflows and enhances flexibility.

### Describe the solution

Allow `testConnection` to work with just `provider` and `properties`, making the catalog name optional.

### Additional context

_No response_

Start by locating the testConnection method and tracing how it currently uses the catalog name, Metalake, provider, and properties. Review the API and validation paths involved, then identify the tests covering connection testing. Done means testConnection can validate a connection with only provider and properties while preserving existing catalog-based behavior.

Written by the indexing model from the issue text.