Boost: Add e2e tests to Page Cache

[dilirity]

Part of #33877

Proposed changes:

• Add e2e tests for the Page Cache module:
  • Meta isn't visible while the module is deactivated;
  • Cache header isn't present while the module is deactivated;
  • There's an error when plain permalinks are used and there's an attempt to activate the module;
  • Meta is visible while the module is activated;
  • Cache header is present while the module is activated.
• Update e2e tests to allow changing permalinks on the site;
• Update Boost CLI to support activating/deactivating Page Cache;
• Update docker e2e test matrix to include tests (you can check the GH actions section to see the tests).

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

n/a

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

no

Testing instructions:

• Run tests to see if everything is working as expected.

[github-actions]

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Boost plugin:

• Next scheduled release: May 7, 2024.
• Scheduled code freeze: April 29, 2024.

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[dilirity]

Ready for review.

This PR needs an update for making relevant parts of the site writable, as wp-config.php and wp-content aren't writable, so tests fail because cache can't be enabled.

I've reached out for help here p1711711037050859-slack-CBG1CP4EN

[haqadn]

Looks good so far, can we have a test where instead of just checking for the cache header, we look for cache-hit? This will cover more areas of the caching.

[dilirity]

@haqadn thanks for the suggestion. I've updated the tests to check the value of the header as well.

[haqadn]

👍🏼