Form navigation update

[jasalisbury]

As a Smart Hub user, I want form navigation to be consistent, so I don't have to think about how I want to navigate the form

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Navigating the form via the side nav or Continue button behave differently. Clicking Continue validates the form and doesn't allow the user to move to the next page until the form is valid. The side nav always allows the user to change the page even if the form is invalid. We want these two forms of navigation to behave the same.

Additional Context
https://gsa-tts.slack.com/archives/C017RJ4GEET/p1614007348000500

Acceptance Criteria

• Clicking Continue moves the user to the next page regardless of the validity of the form
• When the user navigates (Continue or side nav) the current page is marked as complete if the form is valid
• A draft is saved to the API when navigating
• Error messages are shown on page load after the user visits the review page and navigates to a different page