Plans page for Jetpack App: Handle all unhandled jetpack-app/* routes by showing 404 page

[staskus]

Related to #82135

Handle all unhandled jetpack-app/* routes by showing a 404 page

Proposed Changes

• Use EmptyContent component with images, titles, and descriptions from similar empty content components
• Keep default styles
• Reuse existing translations

404.not.found.page.mov

Testing Instructions

• jetpack-app/ should continue routing to jetpack-app/plans
• jetpack-app/plans should continue displaying Plans page with wp-iphone and wp-android user agent
• jetpack-app/* routes should display 404 page

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)?

[github-actions]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-84130

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-84130&env=jetpack

[matticbot]

Here is how your PR affects size of JS and CSS bundles shipped to the user's browser:

Sections (~143 bytes added 📈 [gzipped])

name         parsed_size           gzip_size
jetpack-app       +383 B  (+0.1%)     +143 B  (+0.1%)

Sections contain code specific for a given set of routes. Is downloaded and parsed only when a particular route is navigated to.

Legend

What is parsed and gzip size?

Parsed Size: Uncompressed size of the JS and CSS files. This much code needs to be parsed and stored in memory.
Gzip Size: Compressed size of the JS and CSS files. This much data needs to be downloaded over network.

Generated by performance advisor bot at iscalypsofastyet.com.

[tyxla]

Looks good, and works well. Thanks 🚀