[FEATURE] kyuubi-flink-sql-engine should support scala code like spark-sql-engine

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://www.apache.org/foundation/policies/conduct)

### Search before asking

- [X] I have searched in the [issues](https://github.com/apache/incubator-kyuubi/issues?q=is%3Aissue) and found no similar issues.

### Describe the feature

kyuubi-flink-sql-engine should support scala code like kyuubi-spark-sql-engine

### Motivation

_No response_

### Describe the solution

_No response_

### Additional context

_No response_

### Are you willing to submit PR?

- [ ] Yes I am willing to submit a PR!

Compare the kyuubi-flink-sql-engine and kyuubi-spark-sql-engine entry points to determine how Scala code support is implemented in the Spark engine. Identify the relevant files and tests before defining the required scope; done means the Flink SQL engine supports Scala code in a comparable way.

Written by the indexing model from the issue text.