#7710323 Add email stats for devices & clients

Proposed Changes

This PR adds the data logic & UI for the devices & clients panels in email open stats.

In detail, it:

• Adds the Redux logic (routing/transforming the incoming data from the API to the store)
• Adds the UI for the panel
• Adds a grid layout for email open stats
• Adds titles to the panels
• Does a bit of cleanup:
  • Use <StatsEmailModule> directly, instead of creating a separate proxy component for every stat type
  • Remove the preview code from the <StatsEmailOpenDetail> module

Testing Instructions

• Visit /stats/email/open/<site>/day/<postid>?flags=newsletter/stats. You can add the startDate parameter, to load the stats for a specific date.
• Ensure the cards are rendered:

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)?

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