Fixes https://github.com/payloadcms/payload/issues/6648
This PR introduces a new `useFormBackgroundProcessing` hook and a corresponding `setBackgroundProcessing` function in the `useForm` hook.
Unlike `useFormProcessing` / `setProcessing`, which mark the entire form as read-only, this new approach only disables the Publish button during autosaving, keeping form fields editable for a better user experience.
I named it `backgroundProcessing` because it should run behind the scenes without disrupting the user. You could argue that it is a bit more generic than something like `isAutosaving`, but it signals intent: Background = do not disrupt the user.
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