[Improve][Transform][SQL] Support cast to TINYINT/SMALLINT

[hailin0]

Purpose of this pull request

Does this PR introduce any user-facing change?

How was this patch tested?

Check list

• If any new Jar binary package adding in your PR, please add License Notice according
  New License Guide
• If necessary, please update the documentation to describe the new feature. https://github.com/apache/seatunnel/tree/dev/docs
• If you are contributing the connector code, please check that the following files are updated:
  1. Update plugin-mapping.properties and add new connector information in it
  2. Update the pom file of seatunnel-dist
  3. Add ci label in label-scope-conf
  4. Add e2e testcase in seatunnel-e2e
  5. Update connector plugin_config

[Copilot]

Pull Request Overview

This pull request extends the SQL cast functionality in SeaTunnel to support conversions to TINYINT and SMALLINT.

• Added unit tests in CastFunctionTest.java to verify the new cast behavior.
• Updated SystemFunction.java to handle TINYINT and SMALLINT conversions using Byte.parseByte and Short.parseShort.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
seatunnel-transforms-v2/src/test/java/org/apache/seatunnel/transform/sql/zeta/CastFunctionTest.java	Introduces a new test case validating TINYINT and SMALLINT casts.
seatunnel-transforms-v2/src/main/java/org/apache/seatunnel/transform/sql/zeta/functions/SystemFunction.java	Adds new cases in the cast function to support TINYINT and SMALLINT types.

Comments suppressed due to low confidence (1)

seatunnel-transforms-v2/src/test/java/org/apache/seatunnel/transform/sql/zeta/CastFunctionTest.java:33

• Consider adding edge case tests for invalid or out-of-range values (e.g., non-numeric strings or values exceeding byte/short limits) for TINYINT and SMALLINT casts to improve test coverage.

public void testCastFunction() {

[Hisoka-X]

Please update the doc. Refer https://github.com/apache/seatunnel/pull/9342/files#diff-51bdd641ede50558e18ecf382d94ef347fe697130a9ac47e287b8064d26b196eR760-R779