Settings: Limit popup to existing sites

[lsl]

This PR adds more pop ups for more settings screens.

We should limit who sees any of these pop ups to existing sites only. We can use a future blog id to limit which blogs see the popups and have some overlap.

• Disable educational popups for new sites (code point)

[github-actions]

OpenAI suggested the following labels for this issue:

• [Feature Group] Site Settings & Tools: The issue relates to settings configurations, specifically limiting who sees popups based on site status.
• [Feature] JITM: The issue discusses the management of pop-ups, which are Just In Time Messages used for user interaction and guidance.
• [Feature] User Management: This feature is relevant as limiting popup visibility could impact user management and site onboarding for new sites.

[lsl]

I see this has already been done in wpcom-admin-interface.php