Boost: Add speculation rules

[haqadn]

Proposed changes:

• Add speculative loading module.

[!NOTE]
This is something core is experimenting with and will likely add to core soon. There is also a Speculative Loading plugin from core performance team as part of the experiment. This implementation is similar, but it tries to be more conservative by excluding external URLs, and URLs with query parameter to avoid pitfalls.

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

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

Testing instructions:

• define JETPACK_BOOST_ALPHA_FEATURES as true

• If you are using uBlock origin, uncheck "Disable pre-fetching (to prevent any connection for blocked network requests)"

• Enable "Prerender Pages" from Boost settings

• Go to the front end of the site.

• Hover over any internal URL that and give it a moment before clicking.

• The page should load almost instantly because it's speculatively loading in the background.

[github-actions[bot]]

Thank you for your PR!

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• Next scheduled release: March 3, 2025.

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[github-actions[bot]]

This PR has been marked as stale. This happened because:

• It has been inactive for the past 3 months.
• It hasn’t been labeled `[Pri] BLOCKER`, `[Pri] High`, etc.

If this PR is still useful, please do a [trunk merge or rebase](https://github.com/Automattic/jetpack/blob/trunk/docs/git-workflow.md#keeping-your-branch-up-to-date) and otherwise make sure it's up to date and has clear testing instructions. You may also want to ping possible reviewers in case they've forgotten about it. Please close this PR if you think it's not valid anymore — if you do, please add a brief explanation.

If the PR is not updated (or at least commented on) in another month, it will be automatically closed.

[github-actions[bot]]

This PR has been automatically closed as it has not been updated in some time. If you want to resume work on the PR, feel free to restore the branch and reopen the PR.

[jp-launch-control[bot]]

Code Coverage Summary

1 file is newly checked for coverage.

File	Coverage
projects/plugins/boost/app/modules/optimizations/speculative-loading/Speculative_Loading.php	0/33 (0.00%) 💔

Full summary · PHP report · JS report

_{Add label https://github.com/Automattic/jetpack/labels/I%20don%27t%20care%20about%20code%20coverage%20for%20this%20PR to override the failing coverage check.}

[donnchawp]

Too many failed checks. I already did a merge but it asking for another. I'll just go back to my newer PR.