[Subscription block] Add social followers toggle

[TimBroddin]

Changes proposed in this Pull Request:

This PR adds a toggle to the Subscription block settings, that allows to toggle between including social followers (default) in the count, or excluding them.

Jetpack product discussion
pdDOJh-ZI-p2
pdDOJh-Yp-p2

Does this pull request change what data or activity we track or use?
No

Testing instructions:

1. Apply this PR
2. The checkbox should be visible & toggling it should update the number in both editor & frontend.

To test with simple sites:

• On your sandbox:
  • bin/jetpack-downloader test jetpack add/subscription-block-social-toggle(don't checkout trunk)

To test with Atomic:

• Follow these instructions: pb5gDS-1rQ-p2

Also make sure that users see the same count when upgrading (standard behavior should be to include social followers)

[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:

• ✅ Include a description of your PR changes.
  
• ✅ All commits were linted before commit.
  
• ✅ Add a "[Status]" label (In Progress, Needs Team Review, ...).
  
• ✅ Add testing instructions.
  
• ✅ Specify whether this PR includes any changes to data or privacy.
  
• ✅ Add changelog entries to affected projects
  

This comment will be updated as you work on your PR and make changes. If you think that some of those checks are not needed for your PR, please explain why you think so. Thanks for cooperation 🤖

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Jetpack plugin:

• Next scheduled release: December 6, 2022.
• Scheduled code freeze: November 28, 2022.

[github-actions]

Are you an Automattician? You can now test your Pull Request on WordPress.com. On your sandbox, run bin/jetpack-downloader test jetpack add/subscription-block-social-toggle to get started. More details: p9dueE-5Nn-p2

[mashikag]

The code looks fine to me.
I tested the PR and the added "include social followers" toggle seems to work as expected. 👍

[TimBroddin]

Did some refactoring after seeing that the block & shortcode widget are now decoupled.

This is ready for another team review next week.

[mashikag]

I had another look and the last commit seems to be fixing the issue mentioned by @coder-karen . All looks good to me. 👍

[bindlegirl]

LGTM