Boost: Improve critical css generation process

[dilirity]

This PR fixes the C.CSS generation process breaking when an invalid URL was passed to the critical CSS gen library.

Recommendations will also now be more unique instead of bunched together under one entry on the advanced recommendations page. Previously, if a provider failed and had URLs with a 301, 404 and 500 error, items would be listed under the 500 error (or the most frequent one). Now they all have separate recommendations and can be dismissed individually. In other words, the error_status for providers has been replaced with dismissed_errors and now holds all error types that were dismissed via the UI.

Fixes #41391

Proposed changes:

• Fix invalid URLs passed to critical CSS gen library, resulting in the whole process being broken;
• Add InvalidURLError recommendation and steps on how to address it;
• Add watch command to CSS gen package;
• Fix not reporting non-200 HTTP errors to the user. This means, 404 pages will no longer be used to generate critical css for a group;
• Update advanced recommendations listing, to list recommendations based on provider-error type, instead of just provider.

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?
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Jetpack product discussion

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

Testing instructions:

TBD

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Boost plugin:

• Next scheduled release: March 3, 2025.

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[jp-launch-control]

Code Coverage Summary

Coverage changed in 7 files. Only the first 5 are listed here.

File	Coverage	Δ%	Δ Uncovered
projects/plugins/boost/app/assets/src/js/features/critical-css/lib/critical-css-errors.ts	0/50 (0.00%)	0.00%	13 💔
projects/plugins/boost/app/lib/critical-css/Critical_CSS_State.php	0/99 (0.00%)	0.00%	8 💔
projects/plugins/boost/app/assets/src/js/features/critical-css/more-list/more-list.tsx	0/13 (0.00%)	0.00%	5 💔
projects/plugins/boost/app/assets/src/js/pages/critical-css-advanced/critical-css-advanced.tsx	0/42 (0.00%)	0.00%	4 💔
projects/plugins/boost/app/assets/src/js/features/critical-css/error-description/error-description.tsx	0/14 (0.00%)	0.00%	2 ❤️‍🩹

1 file is newly checked for coverage.

File	Coverage
projects/plugins/boost/app/assets/src/js/features/critical-css/lib/stores/recommendation-types.ts	0/0 (—%) 🤷

Full summary · PHP report · JS report

_{Coverage check overridden by I don't care about code coverage for this PR Use this label to ignore the check for insufficient code coveage. .}