Connector for StarRocks

### Describe the feature

### Is your feature request related to a problem?

Gravitino provides excellent integration for query engines like Trino and Spark, allowing them to use Gravitino as a unified metadata source. However, it currently lacks a dedicated connector for StarRocks.

This means users who manage their metadata in Gravitino and also use the high-performance StarRocks engine must manually duplicate and maintain catalog configurations in both systems. This is redundant, error-prone, and defeats the purpose of having a centralized metadata lake.

### Describe the solution you'd like

A new **StarRocks Connector** should be developed for Gravitino.

This connector would function similarly to the existing Trino connector, allowing users to register a Gravitino instance as a single, unified external catalog within StarRocks. Once connected, all catalogs managed by Gravitino (e.g., Hive, Iceberg, relational databases) would become immediately accessible for querying from StarRocks.

### Why is this a good idea?

1. **True Unified Metadata:** It extends Gravitino's "manage once, use everywhere" philosophy to another major, high-performance query engine.
2. **Simplified Administration:** StarRocks administrators would no longer need to manage individual catalog connections, drastically simplifying configuration and reducing maintenance overhead.
3. **Increased Adoption:** Supporting a popular engine like StarRocks makes Gravitino a more compelling and complete solution for organizations building a modern, heterogeneous data stack.

This feature would be a significant step towards making Gravitino the universal metadata layer for the entire data analytics ecosystem. Thank you for your consideration.

### Motivation

_No response_

### Describe the solution

_No response_

### Additional context

_No response_

Start by locating and reading Gravitino’s existing Trino connector to understand its integration and catalog-mapping approach. Then investigate StarRocks’ external-catalog interface and define the required connector scope; done means Gravitino-managed catalogs are accessible for querying through StarRocks.

Written by the indexing model from the issue text.