isDirty from form groups is broken with array inputs

[ghost91-]

What you were expecting:
When using the FormGroupContextProvider around an ArrayInput, the isDirty property of useFormGroup still is a boolean, as the type definitions indicate.

What happened instead:
When using the FormGroupContextProvider around an ArrayInput, the isDirty property of useFormGroup is broken: When changing the array input, the isDirty property is set to some array that containes information about properties of array elements that have changed. But it should be just a boolean.

Steps to reproduce:

1. Use an ArrayInput inside a FormGroupContextProvider
2. Inside that FormGroupContextProvider, also use a component that uses isDirty via useFormGroup in some way (e.g., by displaying it)
3. Adjust values managed by the ArrayInput, or add/delete items of the ArrayInput
4. Observe that the isDirty property is set to an array, instead of just a boolean.

Related code:
https://codesandbox.io/s/goofy-tess-wzpom6?file=/src/posts/PostEdit.tsx:5416-5440

In the PostsEdit.tsx in the miscellaneous tab, I added a FormGroupContextProvider around the backlinks ArrayInput, which shows the problem.

Other information:

[WiXSL]

Reproduced!
Thanks for the report.