#8363117 Move payment features to under the Free plan

Proposed Changes

Per the request made in pdgrnI-2xq-p2#comment-4128, the following changes are made:

1. Move “Gated content” from under the Personal plan to under the Free plan..
2. The feature “Gated content” is renamed to “Paid content gating” if translation exists.
3. Add “Paid subscribers” under the Free plan.
4. This PR brings parity with the landing page changes done in D115618-code. Verify that the pricing grid UI exactly matches the one seen in wordpress.com/pricing.

Top of the fold:

Below the fold comparison grid

Testing Instructions

• Begin fresh signup at /start. At the plans step /start/plans, verify that the copy changes mentioned in the description are visible.
• Verify in a non-EN locale that all the translations exist.

Pre-merge Checklist

• Has the general commit checklist been followed? (PCYsg-hS-p2)
• Have you written new tests for your changes?
• Have you tested the feature in Simple (P9HQHe-k8-p2), Atomic (P9HQHe-jW-p2), and self-hosted Jetpack sites (PCYsg-g6b-p2)?
• Have you checked for TypeScript, React or other console errors?
• Have you used memoizing on expensive computations? More info in Memoizing with create-selector and Using memoizing selectors and Our Approach to Data
• Have we added the “[Status] String Freeze” label as soon as any new strings were ready for translation (p4TIVU-5Jq-p2)?
• For changes affecting Jetpack: Have we added the “[Status] Needs Privacy Updates” label if this pull request changes what data or activity we track or use (p4TIVU-ajp-p2)?