Avoid query strings for aggregated CSS files (like JS)

Summary

Query strings (eg. ?pjfoi0) should be avoided in URLs of static resources (eg. CSS and JavaScript) as it can cause caching issues.

In some cases, Drupal adds a query string hash to CSS URLs for cache-busting. However, this can be avoided especially when the filename already includes a hash of aggregated CSS contents (eg. css_5r96Ja_jU4_qLNpmi92hAFXhO4WgRT1hcq9JHRbrO5c.css).

Drupal already does this for JavaScript, I propose the same behaviour for CSS.

To reproduce

1. At admin/config/development/performance, enable CSS and JS file aggregation
2. Visit a page as anon and view source

Actual result

• CSS files have a hash in the filename and in a query string
• JS files have a hash in the filename (but no query string)

This can be seen at https://dri.es:

<link rel="stylesheet" href="/sites/default/files/css/css_5r96Ja_jU4_qLNpmi92hAFXhO4WgRT1hcq9JHRbrO5c.css?pjfoi0" media="all" />
<link rel="stylesheet" href="/sites/default/files/css/css_yCk0ufaMqnZTTM6bcwv4yisq5PMm6-bTMscAKOO0UGY.css?pjfoi0" media="all" />
...
<script src="/sites/default/files/js/js_1ufn5cD4yDhD-AhW0q4sUVahgoOMxgCp7H93OfrTKDM.js"></script>

Expected result

• Both CSS and JS files have a hash in the filename (but no query string)

<link rel="stylesheet" href="/sites/default/files/css/css_5r96Ja_jU4_qLNpmi92hAFXhO4WgRT1hcq9JHRbrO5c.css" media="all" />
<link rel="stylesheet" href="/sites/default/files/css/css_yCk0ufaMqnZTTM6bcwv4yisq5PMm6-bTMscAKOO0UGY.css" media="all" />
...
<script src="/sites/default/files/js/js_1ufn5cD4yDhD-AhW0q4sUVahgoOMxgCp7H93OfrTKDM.js"></script>