SAL: Add wpcom_site_setup property to /sites/{siteId} endpoint

[miksansegundo]

Related #31662 Automattic/wp-calypso#78852

Proposed changes:

• Add wpcom_site_setup property to /sites/{siteId} endpoint

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
• Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

• N/A

Does this pull request change what data or activity we track or use?

• No

Testing instructions:

• Sandbox the API
• Make a request to /sites/{siteId}
• Verify the response contains the property wpcom_site_setup in options
  • The value will be false if it's not set, or can be assembler if you are reusing that site

Tested on a Simple site

Tested on an Atomic site

[github-actions]

Are you an Automattician? Please test your changes on all WordPress.com environments to help mitigate accidental explosions.

• To test on WoA, go to the Plugins menu on a WordPress.com Simple site. Click on the "Upload" button and follow the upgrade flow to be able to upload, install, and activate the Jetpack plugin. Once the plugin is active, go to Jetpack > Jetpack Beta > Jetpack and enable the add/wpcom-site-setup-to-sites-endpoint branch.

• To test on Simple, run the following command on your sandbox:

  bin/jetpack-downloader test jetpack add/wpcom-site-setup-to-sites-endpoint
  

Interested in more tips and information?

• In your local development environment, use the jetpack rsync command to sync your changes to a WoA dev blog.
• Read more about our development workflow here: PCYsg-eg0-p2
• Figure out when your changes will be shipped to customers here: PCYsg-eg5-p2

[github-actions]

Thank you for your PR!

When contributing to Jetpack, we have a few suggestions that can help us test and review your patch:

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• ✅ Specify whether this PR includes any changes to data or privacy.
  
• ✅ Add changelog entries to affected projects
  

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The e2e test report can be found here. Please note that it can take a few minutes after the e2e tests checks are complete for the report to be available.

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Jetpack plugin:

• Next scheduled release: July 5, 2023.
• Scheduled code freeze: June 26, 2023.

[miksansegundo]

The e2e tests that are failing are not related to my changes. See p1686869270217619-slack-CBG1CP4EN

[miksansegundo]

The continuous-integration/a8c-teamcity test failing in D115123-code is also unrelated to my changes.

[miksansegundo]

@Automattic/lego can you review these changes, please?