Widget visibility: Make request paths work on wpcom

[dsas]

Part of #20057

This plugin checks the current REQUEST_URI to decide whether or not to
register hooks. The REQUEST_URI it checked against was correct for
WordPress.org sites but not for WordPress.com sites.

These have now been updated to work in both cases.

Builds on #20255 which doesn't work on wp.com simple sites, this has been discussed at p7DVsv-cqD-p2#comment-37158

Changes proposed in this Pull Request:

Made the URL check for when to register hooks weaker.

Jetpack product discussion

Testing instructions:

1. Create a wordpress.com simple site
2. Click on Appearance then widgets in the right hand menu
3. Add a legacy widget

⚠ Note that this still won't work on wp.com unless changes to the eu-cookie-law plugin are applied too

What I expected

A button to control conditional widget visibility as part of the widget form

What happened instead

The widget form without widget visibility button

Does this pull request change what data or activity we track or use?

No.

[github-actions]

Thank you for your PR!

When contributing to Jetpack, we have a few suggestions that can help us test and review your patch:

• ✅ Include a description of your PR changes.
  
• ✅ All commits were linted before commit.
  
• ✅ Add a "[Status]" label (In Progress, Needs Team Review, ...).
  
• ✅ Add testing instructions.
  
• ✅ Specify whether this PR includes any changes to data or privacy.
  
• ✅ Add changelog entries to affected projects
  

This comment will be updated as you work on your PR and make changes. If you think that some of those checks are not needed for your PR, please explain why you think so. Thanks for cooperation 🤖

---

The e2e test report can be found here. Please note that it can take a few minutes after the e2e tests checks are complete for the report to be available.

---

Once your PR is ready for review, check one last time that all required checks (other than "Required review") appearing at the bottom of this PR are passing or skipped.
Then, add the "[Status] Needs Team review" label and ask someone from your team review the code.
Once you’ve done so, switch to the "[Status] Needs Review" label; someone from Jetpack Crew will then review this PR and merge it to be included in the next Jetpack release.

---

Jetpack plugin:

• Next scheduled release: September 7, 2021.
• Scheduled code freeze: August 30, 2021.

[dsas]

the wpcom code has been reviewed on D65394-code which hopefully counts as a team review :)

[jeherve]

This looks good to me. 🚢