fix(transforms): Fix array insertion in field path notation

[ghost]

This PR fixes a bug in the new implementation of field path notation.

When value was inserted in the middle of an array, then instead of replacing the already present value with the same index, it shifted all values to the right. This was not consistent with what we had with in the previous flatten/unflatten implementation.

[github-actions]

Great PR! Please pay attention to the following items before merging:

Files matching src/**:

• For each failure path, is there sufficient context logged for users to investigate the issue?
• Do the tests ensure that behavior is sane for inputs that don't meet normal assumptions (e.g. missing field, non-string, etc)?
• Did you add adequate documentation?

This is an automatically generated QA checklist based on modified files