Test: Dynamic SCSS resolver

[octref]

Test for #58204

• Windows @chrisdias
• macOS @kieferrm
• Linux @gregvanl

Complexity: 1

Overview

Previously, @import 'foo'; or @import './foo' always resolves to ./_foo.scss.
Now @import 'foo'; resolves to one of these five locations (descending order):

• foo.scss
• _foo.scss
• foo/index.scss
• foo/_index.scss
• foo.css

Note that if import relative URL include a leading _ such as _foo or _foo.scss, it only resolves to _foo.scss.
If import relateive URL ends with suffix like .css and .scss, no special resolution is done.

Test

• @import 'foo' can resolve to anyone of these 5 variations, if the other 4 are not present
• When multiple ones are present, such as foo.scss and _foo.scss, resolves to the one higher on the list.