#10555504 Stats: Add feature of Traffic spike forgiveness to the feature list

Related to #85813

Proposed Changes

• Add the feature of traffic spike forgiveness to the Stats Commercial purchase page with an information popover.
• Refactor existing popover styling of the purchase page for reuse.
• Patch the info icon for the fee per unit information.

Testing Instructions

• Apply the latest Diff D129634-code and sandbox public-api.wordpress.com and Store Sandbox.
• Spin this change up on local Calypso.
• Create a new JN site and connect it to Jetpack.
• Navigate to the Commercial purchase page for the new JN site: /stats/purchase/{site-slug}?productType=commercial.
• Ensure the traffic spike forgiveness feature is displayed with an information popover on the feature list.
• Ensure the info icon and popover for the fee per unit information work as previously.

• Purchase the 2M tier and return to the purchase page.
• Ensure the info icon and popover for the fee per unit information are not displayed.

Pre-merge Checklist

• Has the general commit checklist been followed? (PCYsg-hS-p2)
• https://wpcalypso.wordpress.com/devdocs/docs/testing/index.md 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)?