Refactor Etag-based cache busting for styles and scripts solution and add tests

[vrajadas]

Following issue #58433, I wanted to add tests to the solution and then realised they is code duplication. I move the logic to method in the class both wp_script and wp_style extend.

I also added tests.
Test instructions are the same as in #58433, since this issue doesn't change functionality.
Github PR is ​https://github.com/WordPress/wordpress-develop/pull/6820

Added tests to change make in PR for ​58433

Moved the logic to a separate method under wp-dependencies class and added unit tests.

Trac ticket: https://core.trac.wordpress.org/ticket/61485

Hey @peterwilsoncc I created a new trac ticket and updated the PR description with it's new number.

@mukeshpanchal27 would you please re-review this task?

[mukesh27]

The PR looks good to me and approved, happy to get more folks eye.

Move to 6.7 milestone.

[peterwilsoncc]

In 58935:

Script Loader: Refactor Etag generation for concatenated assets.

Move Etag HTTP header generation in load-scripts.php and load-styles.php to WP_Dependencies.

Introduces the method WP_Dependencies::get_etag() and associated unit tests.

Follow up to [57943].

Props vrajadas, martinkrcho, mukesh27.
Fixes #61485.

Merged r58935 / ​https://github.com/WordPress/wordpress-develop/commit/a3520d2720f6d434b78346dd53cb38ec88c74bcb

[swissspidy]

Bug identified that was introduced here: ​https://github.com/WordPress/wordpress-develop/pull/7715

cc @peterwilsoncc

[SergeyBiryukov]

In 59341:

Script Loader: Correct the number of arguments passed to WP_Styles::get_etag().

This fixes an issue with the usage of the new $wp_styles->get_etag() method in wp-admin/load-styles.php, where $wp_version is passed as the first argument instead of $load being used as the only argument.

Follow-up to [58935].

Props justlevine, mukesh27, swissspidy.
See #52217, #61485.

[SergeyBiryukov]

Reopening for merging [59341] to the 6.7 branch after a second committer's review.

[peterwilsoncc]

In 59343:

Script Loader: Correct the number of arguments passed to WP_Styles::get_etag().

This fixes an issue with the usage of the new $wp_styles->get_etag() method in wp-admin/load-styles.php, where $wp_version is passed as the first argument instead of $load being used as the only argument.

Follow-up to [58935].

Reviewed by swissspidy.
Merges [59341] to the 6.7 branch.

Props justlevine, mukesh27, swissspidy, SergeyBiryukov.
See #52217, #61485.

[desrosj]

This seems to have been appropriately addressed, the commit message just lacked a Fixed line.

Closing out, but please reopen if I'm missing something.