Closes #6137: remove unnecessary exclusions css background images' lazyload

[Miraeld]

Description

We deleted the unnecessary filters for css exclusions for background images' lazyload.
We also deleted linked tests.

Fixes #6137

Type of change

• Enhancement (non-breaking change which improves an existing functionality).

Is the solution different from the one proposed during the grooming?

No

Checklists

Generic development checklist

• My code follows the style guidelines of this project, with adapted comments and without new warnings.
• [] I have added unit and integration tests that prove my fix is effective or that my feature works.
• The CI passes locally with my changes (including unit tests, integration tests, linter).
• Any dependent changes have been merged and published in downstream modules.
• If applicable, I have made corresponding changes to the documentation. Provide a link to the documentation.

Test summary

• I triggered all changed lines of code at least once without new errors/warnings/notices.
• I validated all Acceptance Criteria of the related issues. (If applicable, provide proof).
• I validated all test plan the QA Review asked me to.

[wordpressfan]

Nice job.

I don't think that we need to deprecate those public methods as it's not used by any of our helpers (I checked that)

Also just an explanation, in backend we exclude rocket_lazyload_css_data which is a keyword that is contained inside #rocket_lazyload_css-js-after script, so we are fine.

[Mai-Saad]

Working as expected
testrail-report-532.pdf
Note (problems already on 3.15.2)
1- Images using this markup will be removed from the page => agreed as edge case
<style>.test-new-class{background-image: url("https://new.rocketlabsqa.ovh/wp-content/rocket-test-data/images/test_internal2.jpg");}.test-new-class{background-image: url("/wp-content/rocket-test-data/images/wp-rocket.svg)");} </style>
Thanks to @vmanthos investigations

The syntax of the following is incorrect:
background-image: url("/wp-content/rocket-test-data/images/wp-rocket.svg)");
There is a ) before " and that results in WP Rocket picking up the whole thing until the last parenthesis.

2- Problem when LL BGI is enabled while WPML is on (under investigation to gather reproducible steps)(happening with CSS absolute URL files)

• Using rocketlabs env, if we have WPML activated on domain base setup, then install /activate WPR, then cache LL BG template, then enable LL BG I then access the sub language FE and hardrefresh => We will have console error for some images
  
• Console error when trying to switch language in the following steps:
  1- WPML is domain base
  2- cache the page in both languages
  3- WPML changed to a directory
  4- access the main language page and click on language switch to sub-lang
  
  if we clear the whole cache then repeat step 4 it will work fine

[vmanthos]

@Mai-Saad I was able to reproduce the issue on rocketlabsqa.ovh. However, clearing the cache won't fix it.

For CSS files processed by the lazyload for background CSS images feature, we set the wrong path, resulting in error 404 for those files. This is because we are adding the language code before the domain name.

For example:
https://ar.rocketlabsqa.ovh/wp-content/cache/background-css/ar.ar.rocketlabsqa.ovh/wp-content/cache/min/1/wp-content/rocket-test-data/styles/lazyload_css_background_images.css?ver=1697180904&wpr_t=1697180904

has an extra ar. before the TLD ar.rocketlabsqa.ovh.

The URL should be:

https://ar.rocketlabsqa.ovh/wp-content/cache/background-css/ar.rocketlabsqa.ovh/wp-content/cache/min/1/wp-content/rocket-test-data/styles/lazyload_css_background_images.css?ver=1697180904&wpr_t=1697180904
https://ar.rocketlabsqa.ovh/wp-content/cache/background-css/ar.ar.rocketlabsqa.ovh/

Update

I believe this should be on a new GitHub issue.

[Mai-Saad]

@vmanthos Thanks for the confirmation, added GH here #6224

However, clearing the cache won't fix it.

This was for the second scenario, related to xdomaindata console error when switching language