Stats: Fix purchase page for site-less flow

[dognose24]

Related to p1729743194369679-slack-C1T3N5AMR

Proposed Changes

• Revert the change of wrapping StatsPurchasePage with StatsPageLoader where we check site access permissions because it would forbid site-less purchases.

Why are these changes being made?

• The site-less Stats purchase flow was not accessible because of the permission check in StatsPageLoader. The purchase page should be open to visiting without selected sites.

Testing Instructions

• Spin this change up with the Calypso Live branch.
• Navigate to the Stats purchase page without selected sites: /stats/purchase.
• Ensure the purchase page displays.

• Click the Get Stats to grow my site button to purchase the license.
• Ensure the redirecting checkout page is running for a site-less purchase flow: https://wordpress.com/checkout/jetpack/jetpack_stats_yearly

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-aUh-p2)?

[github-actions]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-122630

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-122630&env=jetpack

Automattic for Agencies live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-122630&env=a8c-for-agencies

[matticbot]

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

Sections (~1 bytes added 📈 [gzipped])

name   parsed_size           gzip_size
stats        -23 B  (-0.0%)       +1 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.

Async-loaded Components (~10 bytes added 📈 [gzipped])

name                                              parsed_size           gzip_size
async-load-calypso-my-sites-stats-pages-purchase        +83 B  (+0.1%)      +10 B  (+0.1%)

React components that are loaded lazily, when a certain part of UI is displayed for the first time.

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.

[a8ck3n]

Tests well for me. Thanks @dognose24!