Apply AdaptiveForm and its abilities to steps 2 and 3 of the onboarding flow for higher code consistent

[eason9487]

Changes proposed in this Pull Request:

With #2014, this is another pre-processing PR for #634 and for 📌 Display form validation errors in #1993.

To apply AdaptiveForm and its abilities to steps 2 and 3 of the onboarding flow, and make the uses of formContext ( the former formProps) higher consistent, this PR:

• Change to use the adapter.isSubmitting of AdaptiveForm as the loading state of submit button in SetupFreeListings and StoreRequirements
• Apply useAdaptiveFormContext instead of formProps prop drilling for SetupFreeListings and the relevant components.
• Apply AdaptiveForm and useAdaptiveFormContext instead of Form and formProps for StoreRequirements and the relevant components
• Extend the adapter to avoid audienceCountries prop drilling for SetupFreeListings and the relevant components.

💡 It's possible to continue the subsequent implementation without this PR, but the uses of form and the relevant states will become scattered and more difficult to maintain. Therefore, I would like to tweak the codebase first.

Detailed test instructions:

This PR only changes the code used in steps 2 and 3 of the onboarding flow but doesn't change the UI behaviors.

1. Go to step 2 of the onboarding flow.
2. Repeatedly fill in and clean up the audience countries and shipping settings.
3. Check if the form-related behaviors are still the same as before.
4. Proceed to step 3.
5. Similar to above, check if the form-related behaviors are still the same as before.
6. Click "Continue" button to go to step 4 and see if the loading state work well.

The SetupFreeListings component is used in the Edit free listings page as well.

1. Go to the Edit free listings page.
2. Repeatedly fill in and clean up the audience countries and shipping settings.
3. Check if the form-related behaviors are still the same as before.
4. Click "Save changes" button and see if the loading state work well.

Changelog entry

[ianlin]

Thanks for the refactoring, it looks much cleaner by removing prop drilling. The form behaviour in onboarding steps and edit free listing pages work as expected, LGTM.