[FLINK-6926] [table] Add support for SHA-224, SHA-384, SHA-512

[genged]

What is the purpose of the change

This pull request implements SHA224, SHA384, SHA512 support in Flink SQL as discussed in FLINK-6926

Brief change log

• Added SHA224, SHA384, SHA512 SQL functions
• Added relevant unit tests

Verifying this change

This change added tests and can be verified as follows:

• Added SQL expression tests
• Added HashFunctionsTest with testAllApis
• Validated both correct calculation and behavior for null input

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): no
• The serializers: don't know
• The runtime per-record code paths (performance sensitive): don't know
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Yarn/Mesos, 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

[twalthr]

Thanks for the PR @genged. The overall code looks good, however, it seems that databases like MySQL make the bit length configurable (https://dev.mysql.com/doc/refman/5.5/en/encryption-functions.html#function_sha2). We should support SHA2(string, length) instead of SHA224(string) to be compliant with other SQL vendors.

[genged]

@twalthr Added support for SHA2 as per your request. I also left support for using SHA224, SHA256, SHA384, SHA512 functions directly.

[twalthr]

Thank you @genged. I will have a final pass over the code and merge this.