Issue #3088805 by huzooka, martin107, lauriii, xjm: Simplify Claro's CSS directory structure

core/tests/Drupal/FunctionalTests/Theme/ClaroTest.php

core/themes/claro/claro.info.yml

core/themes/claro/claro.libraries.yml

core/themes/claro/css/base/elements.css

core/themes/claro/css/base/elements.pcss.css

core/themes/claro/css/base/print.css

core/themes/claro/css/base/print.pcss.css

core/themes/claro/css/base/typography.css

core/themes/claro/css/base/typography.pcss.css

core/themes/claro/css/base/variables.css

core/themes/claro/css/base/variables.pcss.css

core/themes/claro/css/components/accordion.css

core/themes/claro/css/components/accordion.pcss.css

core/themes/claro/css/components/action-link.css

core/themes/claro/css/components/action-link.pcss.css

core/themes/claro/css/components/ajax-progress.module.css

...themes/claro/css/components/ajax-progress.module.pcss.css

...emes/claro/css/components/autocomplete-loading.module.css

...claro/css/components/autocomplete-loading.module.pcss.css

core/themes/claro/css/components/breadcrumb.css