Plans overhaul: Add Google Analytics for Starter #7320581

Changes proposed in this Pull Request

1. Adds the Google Analytics feature to the plans grid
2. Adds the Google Analytics feature block to plans/my-plan
3. Adds the Google Analytics feature block to the checkout thank-you page

(this will also be included in the about-to-be-obsolete “free vs pro” grid, but I guess that’s fine – it will just be marked with “not included”)

Media

start/plans

plans/my-plan

Testing instructions

• Go to /start/plans and select “show full plan comparison”
  • confirm feature is included in list as in media above
• Go to /plans/[SITE_ON_FREE_OR_STARTER] and select “show full plan comparison”
  • confirm feature is included in list as in media above
• Go to /plans/my-plan/[SITE_ON_STARTER] and confirm a GA block is there
  • Click on it and confirm the form that opens is working as expected (the backend parts should be in place)
• Go to /start/plans and purchase a Starter plan. Complete the checkout
  • Confirm the “thank you” page includes a block with GA info (same as with Pro)
• Disable the flag (e.g. /start/plans?flags=-plans/starter-plan) and ensure nothing breaks.
  • The GA feature should still be in the list, and marked as “not included” for the free plan. (assuming this is ok)

TODO

• Let’s reorder the features list and make any other contextual updates to the list in this PR. Not sure if the final order has been settled yet. See Slack thread: p1652878563789739/1652865158.458459-slack-C031TFM2NKC
• Let’s update the subtitle of the Starter plan also once it’s finalized/settled. Same Slack thread: p1652878563789739/1652865158.458459-slack-C031TFM2NKC

Related to Automattic/martech#741
Fixes Automattic/martech#741