Themes: sheet Support logic changes to include Jetpack

[folletto]

The blocks in "Support" should follow this logic:

1. Contact us — shown only if “Paid” and “Not Jetpack”
2. Theme forum (Premium) — shown only if “Premium theme”
3. Theme forum (general) — shown only if “.com theme” and “not Premium theme”
4. CSS Support — shown only if “.com theme”

/ht @annezazuu @andrewspittle @jeherve @rachelsquirrel

[folletto]

Done in #11294.

For future reference, we did some minor clarifications to the logic:

• If isCurrentUserPaid and not isJetpack → show "Contact us"
• If the theme has forumUrl and:
  • isPremium → theme shop forum
  • not isPremium → volunteer and staff forum
• If the theme isWpcomTheme → show "CSS Support" (both for .com and JP sites)

Also we added:

• If the user is isLoggedIn but none of the conditions above → show "Unsupported"
• If the user is not isLoggedIn → show "Have a question"