Add-ons: Make isAddOn property optional

[jeyip]

Related to #79041 (comment) and https://github.com/Automattic/martech/issues/2023

Proposed Changes

Testing Instructions

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-85247

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-85247&env=jetpack

[matticbot]

This PR modifies the release build for the following Calypso Apps:

For info about this notification, see here: PCYsg-OT6-p2

• editing-toolkit
• happy-blocks
• odyssey-stats

To test WordPress.com changes, run install-plugin.sh $pluginSlug update/storage-option-type on your sandbox.

[matticbot]

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

App Entrypoints (~4 bytes removed 📉 [gzipped])

name           parsed_size           gzip_size
entry-stepper        -77 B  (-0.0%)       -4 B  (-0.0%)
entry-main           -77 B  (-0.0%)       -4 B  (-0.0%)

Common code that is always downloaded and parsed every time the app is loaded, no matter which route is used.

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.