Super Cache: modify advanced-cache.php notice to say Boost Cache module can be disabled

[donnchawp]

If the advanced-cache.php created by Jetpack Boost is found, the plugin displays a warning message saying that Boost must be deactivated before WP Super Cache can be used. This PR changes that message to say that only the Cache module of Boost must be disabled.
With that done, and on refreshing that page WPSC can be configured. We send a message to Boost to let it know the move was successful.

ref: #37227

Proposed changes:

• add a new file inc/boost.php to hold Boost related functionality.
• The notice and tracking code is in this file.
• Load that notice from wp-cache.php
• Replace the original warning message with the updated the one.

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
• Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

pc9hqz-2QH-p2

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

Testing instructions:

• Apply this PR using the beta plugin
• Activate Jetpack Boost and enable the Cache module.
• From the Plugins page, activate WP Super Cache.
• Go to the WP Super Cache settings page and note the new notice that says Boost was found.
• Although the notice says that the Cache module can be disabled, that is not the case right now. JB must be disabled.
• Refresh the page with the notice, and it will reload into the "Easy" settings page of the plugin.
• Visit the Boost settings page. The Cache module will be disabled but show a warning about the advanced-cache.php

Before:

After:

[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.
  
• ✅ 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 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 reviewed, it can then be merged.
If you need an extra review from someone familiar with the codebase, you can update the labels from "[Status] Needs Team Review" to "[Status] Needs Review", and in that case Jetpack Approvers will do a final review of your PR.

---

Super Cache plugin:

• Next scheduled release: June 4, 2024.
• Scheduled code freeze: May 27, 2024.

If you have any questions about the release process, please ask in the #jetpack-releases channel on Slack.

[haqadn]

p1716371347024369-slack-C016BBAFHHS

[haqadn]

Looks good 👍🏼