Fix ArrayInput makes edited form always dirty on input blur

[WiXSL]

Fixes #8258

PROBLEM

SaveButton enable state may be true, even though no inputs have been changed.

This is because useFormState().isDirty might differ from useFormState().dirtyFields (react-hook-form/react-hook-form#4740)
This is the expected behavior of react-hook-form and it may happen when you have a missing defaultValue for one of the inputs

· dirtyFields will mark the field dirty or not individually.
· isDirty will always do a deep equal against your defaultValues to determined form is dirty or not.
react-hook-form/react-hook-form#7860 (reply in thread)

This is key, since defaultValue prop might be undefined, and in some cases you end up with isDirty being true but dirtyFields being an empty object. Like in the test I've added in this PR, plus the ones I've fixed in this PR

SOLUTION

Use useFormState().dirtyFields to enable/disable SaveButton instead of useFormState().isDirty

[slax57]

The fix seems good to me!
Nice job digging the issue out of RHF's repo.

Still, I'd be more confident having a second review by @fzaninotto on this one. I'll request it.

[fzaninotto]

Nice work!