postgreSql support regexp_split_to_table function

## Feature Request

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

regexp_split_to_table is not supported when i use shardingsphere 5.4.1

### Describe the feature you would like.

regexp_split_to_table can be used in sql

Start by reproducing a PostgreSQL query using regexp_split_to_table in ShardingSphere 5.4.1 and trace where the SQL is rejected or mishandled. Locate the relevant PostgreSQL SQL parsing or processing tests, then confirm that the function is accepted and behaves correctly in the supported SQL path.

Written by the indexing model from the issue text.