[FLINK-35963][table] Add REGEXP_SUBSTR function

[dylanhz]

What is the purpose of the change

Add REGEXP_SUBSTR function.
Examples:

> SELECT REGEXP_SUBSTR('Steven Jones and Stephen Smith are the best players', 'Ste(v|ph)en');
 Steven
> SELECT REGEXP_SUBSTR('Mary had a little lamb', 'Ste(v|ph)en');
 NULL

Brief change log

FLINK-35963

Verifying this change

RegexpFunctionsITCase#regexpSubstrTestCases

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): (no)
• The public API, i.e., is any changed class annotated with @Public(Evolving): (yes)
• The serializers: (no)
• The runtime per-record code paths (performance sensitive): (no)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: (no)
• The S3 file system connector: (no)

Documentation

• Does this pull request introduce a new feature? (yes)
• If yes, how is the feature documented? (docs)

[flinkbot]

CI report:

• 76f2789 Azure: SUCCESS

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[luotianyou349]

Wow！

[dylanhz]

Share cache among all regexp functions.