Deprecation warnings from Sass about import

**Describe the bug**

With recent update to sass 1.80 we get another wave of deprecations, now about the import rules: https://sass-lang.com/d/import

```
DEPRECATION WARNING: Global built-in functions are deprecated and will be removed in Dart Sass 3.0.0.
Use map.get instead.

More info and automated migrator: https://sass-lang.com/d/import
```

```
DEPRECATION WARNING: Sass @import rules are deprecated and will be removed in Dart Sass 3.0.0.

More info and automated migrator: https://sass-lang.com/d/import
```

As they are just warnings, and are only meant to affect Sass from version 3.0 (they haven't released 2.0 still), we can likely ignore it for now.

Our own setup makes those warnings quite verbose though. By default sass only shows them 5 times per stylesheet being built, but we build many (standalone) stylesheet, multiplying those warnings into dozens (or hundreds even).

We should reduce or silence them on our end. But also would be good to find out if it would be simple enough to migrate. They seem to provide some migration tool: https://sass-lang.com/d/import

Start by reviewing the Sass build setup that compiles the standalone stylesheets and reproduce the warnings with Sass 1.80. Determine whether the warnings should be reduced or silenced, and assess the linked Sass migration guidance; done means the build no longer produces the excessive deprecation output or the affected imports are migrated.

Written by the indexing model from the issue text.