Add “Cancel” button in User Input page

[kuasha420]

Feature Description

For the updated User Input, it was decided to make answering the question entirely "Optional" for the user during any part of the flow. Therefore, there should be a "Cancel" button added to the User Input Page.

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Acceptance criteria

• The User Input page should implement a Cancel button as seen on the design.
• It should be available on all the questions page as well as the Review page.
• Clicking on it should take the user back to Site Kit Dashboard.

Implementation Brief

Test Coverage

QA Brief

Changelog entry

[aaemnnosttv]

As mentioned in https://github.com/google/site-kit-wp/issues/5888#issuecomment-1276720590, I think this could fall under the issue to implement the design since it is a small detail, although it would be good to call out specifically.

[kuasha420]

@aaemnnosttv Can you close this one in favor of #5890 ?

[aaemnnosttv]

Closing in favor of #5890