#7472753 Newsletter: set flow foundation

Proposed Changes

This rearranges the current Newsletter flow (still under construction) to match the Figma. Alongside the basic changes of shuffling things around this also:

1. Unifies the flow names in /start and /stepper to be newsletter (no ‘s’)
2. Adjusts the current intro step with the new wording for Newsletter and Link in bio
3. Adds 2 placeholder steps processingFake and subscriber

This is missing the checkout loading step after purchase. I will remove this when its added.

Testing Instructions

1. Pull branch and yarn start
2. Start at the beginning of the flow http://calypso.localhost:3000/setup?flow=newsletter

• test with logged in and logged out
• test purchase and free plan

3. Check the other /start flow to make sure there was no regression

Pre-merge Checklist

• 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)?