#6305206 Generalize marketplace thank you content

Changes proposed in this Pull Request

• This PR refactors the code in the MarketplaceThankYou component added in #52655 such that the same file exposes a more general ThankYou component that supports the original use case as well as a new page we want to build for Professional Email (aka Titan).
• At present this is still an initial exploration, but it may be close to where we want to land for our first iteration.
• One area that may make sense for the support area is to allow for more specific text and/or links to be supplied, but that should be easy to take on separately.

Testing instructions

There are two things we need to test:

1. The original Yoast purchase flow, and
2. The visuals for the new Professional Email page

For (1), I would love to get some confirmation from @jdc91 that the testing approach from #52655 is still valid. I kicked the tires here by navigating to /marketplace/thank-you/:siteSlug for an Atomic site where I manually installed the Yoast plugin, and that seemed to work, but I have no idea if that’s valid!

For (2), the visual work is incomplete for now, as I used the same image and didn’t wire in all the relevant checks yet, but you can take a look at the visuals by accessing /email/:domain/titan/thank-you/:siteSlug on a site with a domain.