Allow multiline css declarations in less files for increased readability

[hostep]

Preconditions

1. Have a file test1.less like this:

   & when (@media-common = true) {
   .lib-icon-font(
       @icon-camera__content,
       @_icon-font: @icons-admin__font-name,
       @_icon-font-size: @image-gallery-placeholder-icon__size,
       @_icon-font-color: @image-gallery-placeholder-icon__color,
       @_icon-font-text-hide: true
   );
   }

2. Have a file test2.less like this:

   & when (@media-common = true) {
   .lib-icon-font(@icon-camera__content, @_icon-font: @icons-admin__font-name, @_icon-font-size: @image-gallery-placeholder-icon__size, @_icon-font-color: @image-gallery-placeholder-icon__color, @_icon-font-text-hide: true);
   }

3. See that the contents of these 2 files are the same, it's just the formatting of the code that's different

Steps to reproduce

1. Run vendor/bin/phpcs -s --standard=Magento2 test*.less

Expected result

1. Both files should show no errors

Actual result

1. Getting this output:

   
   FILE: test1.less
   -------------------------------------------------------------------------------------------------------------------------
   FOUND 0 ERRORS AND 4 WARNINGS AFFECTING 4 LINES
   -------------------------------------------------------------------------------------------------------------------------
   4 | WARNING | Expected 1 space after colon in style definition; newline found
   |         | (Magento2.Less.ColonSpacing.AfterNewline)
   5 | WARNING | Expected 1 space after colon in style definition; newline found
   |         | (Magento2.Less.ColonSpacing.AfterNewline)
   6 | WARNING | Expected 1 space after colon in style definition; newline found
   |         | (Magento2.Less.ColonSpacing.AfterNewline)
   7 | WARNING | Expected 1 space after colon in style definition; newline found
   |         | (Magento2.Less.ColonSpacing.AfterNewline)
   -------------------------------------------------------------------------------------------------------------------------

Time: 78ms; Memory: 6MB

### Discussion
In my opinion, the formatting of the code in file `test1.less` is a lot more readable then in file `test2.less`. Coding standards shouldn't recommend to make code less readable.
Also, Magento [uses this syntax as well in its own code](https://github.com/magento/magento2/blob/8ea62ab9374a9e14a9ffe615aceedff745d80077/app/design/adminhtml/Magento/backend/web/css/source/components/_file-uploader.less#L274-L280) and is thus violating its own coding standards ...

This was already reported before, but just [in a comment](https://github.com/magento/magento-coding-standard/issues/395#issuecomment-1503527962) on another issue, now it has its own proper issue which might make it faster to get picked up?

[m2-assistant[bot]]

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