[Feature] Feature/3287 - Enable Generating Arrays Inside JSON for Grouped Values

[vdwals]

Description:
This pull request introduces the ability to generate arrays inside a generated JSON, providing enhanced flexibility for handling grouped values. This addresses #3287

Changes:

1. New Flag: A new flag has been added to the initial settings screen, with a default value of 'false.' This addition ensures backward compatibility, as existing jobs remain unaffected.
2. Modified JSON Result for Grouped Values: Previously, when generating a JSON result for grouped values, the output was an array of JSON objects collected per group. With this update, if the flag is activated, the new result will create a single JSON result in the case of grouping. Inside this element, all non-grouping key fields will be collected in an array.
3. No Additional Dependencies: These changes do not introduce any additional external dependencies.
4. Preservation of Current Behavior: Importantly, these modifications do not alter the current behavior, ensuring compatibility with existing workflows.

These changes enhance the versatility of JSON generation while maintaining compatibility with previous configurations.

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[mattcasters]

It would be great if you could add an integration test for this transform. Perhaps add it to number 68:

https://github.com/apache/hop/tree/master/integration-tests/transforms

This way we can lock in the new functionality. If you suspect an impact on other functionality, more than 1 test would be appreciated.

[hansva]

Awesome work! sorry about the delay!