Cleans up AIO's Sass files by: * Switching them all over to the `@use`-based API from Angular Material. * Removing the import of the Material theming API in a bunch of places that weren't using it. * Migrating the new usages of Sass utility functions to the new syntax (e.g. `map.get` vs `map-get`). * Fixing a few files that were using 4 spaces for indentation instead of 2. PR Close #42442