feat: allow array_group_by to group object rows

[syawqy]

Description

Fixes #10225.

This PR updates array_group_by() so it can group rows that are objects, such as rows returned by json_decode() or object-based result sets.

Previously, the internal grouping helper required each row to be an array and used dot_array_search(), which also only accepts arrays. That caused a type error when grouping an array of stdClass objects.

The change keeps the public helper API unchanged and adds internal dot-path lookup support for array/object rows. Grouped rows are preserved as their original type, so object rows remain objects in the result.

Regression tests were added for:

• Grouping stdClass rows by a direct property.
• Grouping object rows by a nested dot path.

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value (without duplication)
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[mergeable]

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[patel-vansh]

Thanks for the PR. I think object handling in array helper's dot syntax is not being implemented anywhere in the ArrayHelper. I don't know if its indented or not, but if this PR gets merged, we would require follow-up PRs for other methods as well.

[michalsn]

Thank you for sending a PR. Unfortunately, it cannot be merged in its current form.

Since this would be an enhancement rather than a bug fix, it should target the 4.8 branch. Also, as mentioned above, support for arrays of objects should be considered consistently across the other array methods/helpers that currently support only arrays of arrays.