feat: json_merge expression and sql function

[lkm]

Description

This add a new json_merge expression which takes two or more arguments to merge into a single json structure. It also added the corresponding SQL function. This is useful for transforming data in druid, for instance I use it for flattening arrays of objects using fold, e.g. fold((a, acc) -> json_merge(acc, json_object(json_value(a, '$.key'), json_value(a, '$.value'))), arrayofkv, json_object())

Fixed the bug ...

Renamed the class ...

Added a forbidden-apis entry ...

Release note

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Key changed/added classes in this PR

• json_merge expression function
• json_merge sql function

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This PR has:

• been self-reviewed.
  • using the concurrency checklist (Remove this item if the PR doesn't have any relation to concurrency.)
• added documentation for new or modified features or behaviors.
• a release note entry in the PR description.
• added Javadocs for most classes and all non-trivial methods. Linked related entities via Javadoc links.
• added or updated version, license, or notice information in licenses.yaml
• added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• added unit tests or modified existing tests to cover new code paths, ensuring the threshold for code coverage is met.
• added integration tests.
• been tested in a test Druid cluster.

[abhishekagarwal87]

@lkm - There are compilation failures. You may have to rebase your PR too.

[lkm]

@lkm - There are compilation failures. You may have to rebase your PR too.

It seems things have shifted in master since I did this originally. Will resolve those problems soon

[lkm]

@abhishekagarwal87 I think we're good to go now.

[abhishekagarwal87]

Thank you for your contribution @lkm

[lkm]

Thank you for your contribution @lkm

Thanks for merging!