[ISSUE-5130][EC-JDBC] Map NUMERIC columns to decimal

[hutiefang76]

What is changed?

This PR fixes PostgreSQL numeric column metadata mapping in the JDBC engine plugin. PostgreSQL reports numeric columns as java.sql.Types.NUMERIC, but JDBCHelper.getTypeStr only mapped Types.DECIMAL to Linkis decimal, leaving NUMERIC as null.

The value extraction path already handles Types.NUMERIC and Types.DECIMAL together, so this change applies the same mapping in the type-name conversion path.

Why?

Fixes #5130.

Tests

• Reproduced with mvn -pl linkis-engineconn-plugins/jdbc -am -Dtest=org.apache.linkis.manager.engineplugin.jdbc.executor.JDBCHelperTest -Dsurefire.failIfNoSpecifiedTests=false test: failed before the fix with expected: <decimal> but was: <null>.
• Passed after the fix with the same command.
• Passed JDBC unit test set with mvn -pl linkis-engineconn-plugins/jdbc -am -Dtest=ConnectionManagerTest,ProgressMonitorTest,JDBCErrorCodeSummaryTest,JDBCHelperTest,JdbcParamUtilsTest,JDBCMultiDatasourceParserTest -Dsurefire.failIfNoSpecifiedTests=false test (13 tests).

Note: direct mvn -pl linkis-engineconn-plugins/jdbc test cannot resolve unpublished Linkis 1.9.0 reactor artifacts from the configured mirror in this local environment, so the verified commands use -am to build required modules from source.