feat: move general imports to specific scss files (#32121)

This moves XModule scss imports to the specific files where they are required instead of
having a common XModule scss import list.

This is part of  https://github.com/openedx/edx-platform/issues/31624

lms/static/sass/course/courseware/_sidebar.scss

@@ -1,3 +1,5 @@
+@import 'bourbon/bourbon';
+
 .course-index {
   @include transition(all 0.2s $ease-in-out-quad 0s);
   @include border-right(1px solid $border-color-2);

xmodule/css/capa/display.scss

@@ -18,6 +18,7 @@
 // * +Problem - Choice Text Group
 // * +Problem - Image Input Overrides
 // * +Problem - Annotation Problem Overrides
+@import 'bourbon/bourbon';
 
 // +Variables - Capa
 // ====================

xmodule/css/html/display.scss

@@ -1,3 +1,5 @@
+@import 'bourbon/bourbon';
+
 // HTML component display:
 * {
   line-height: 1.4em;

xmodule/css/tabs/tabs.scss

@@ -130,10 +130,6 @@
     padding: 0;
     border: none;
   }
-
-  .blue-button {
-    @include blue-button;
-  }
 }
 
 

xmodule/css/video/display.scss

@@ -8,6 +8,7 @@
 // --------
 // Defaults: what displays if the icon font doesn't load.
 // --------
+@import 'bourbon/bourbon';
 
 // the html target is necessary for xblocks and xmodules, but works across the board
 

xmodule/static_content.py

@@ -147,10 +147,8 @@ def _write_styles(selector, output_root, classes, css_attribute):
         for class_ in classes:
             css_imports[class_].add(fragment_name)
 
-    module_styles_lines = [
-        "@import 'bourbon/bourbon';",
-        "@import 'lms/theme/variables';",
-    ]
+    module_styles_lines = []
+
     for class_, fragment_names in sorted(css_imports.items()):
         fragment_names = sorted(fragment_names)
         module_styles_lines.append("""{selector}.xmodule_{class_} {{""".format(