Plugin update manager: Make eligibility checks more async

[TimBroddin]

Closes #88416

Proposed Changes

• Extends the useIsEligibleForFeature hook with the logic to calculate if the site is eligble
• Gets rid of the spinner on index.tsx
• Only show the eligibility notice after everything is loaded

Atomic	Creator non-atomic	Explorer

Testing Instructions

1. Apply the PR
2. Check for regressions

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-aUh-p2)?

[github-actions]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:commit-d8d67591505e7a698867a24b396e0c4c5dda6977

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:commit-d8d67591505e7a698867a24b396e0c4c5dda6977&env=jetpack

[matticbot]

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

Sections (~16 bytes added 📈 [gzipped])

name                             parsed_size           gzip_size
plugins                               +128 B  (+0.0%)      +16 B  (+0.0%)
jetpack-cloud-plugin-management       +128 B  (+0.0%)      +16 B  (+0.0%)

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.

[bogiii]

You did a good job of cleaning up the entry component logic.
I've tested with the different site plans, and it seems there are no regressions.

👍

[ouikhuan]

Tested with:

• Simple site -> upgrade to Creator plan -> transfer to Atomic
• Atomic
• Jetpack site
• Sites with Explorer plan

All works as expected, nice job 👍