Consolidate sass for Design Management

Ensures all design management sass is
not scattered across multiple files

ee/app/assets/stylesheets/components/design_management/design.scss

+.design-detail {
+  background-color: rgba($black, 0.9);
+
+  .with-performance-bar & {
+    top: 35px;
+  }
+}
+
 .design-presentation-wrapper {
   top: 0;
   left: 0;
@@ -13,11 +21,6 @@
   transform: translateX(-50%);
 }
 
-.design-list-item .design-event {
-  top: $gl-padding;
-  right: $gl-padding;
-}
-
 .design-checkbox {
   position: absolute;
   top: $gl-padding;

ee/app/assets/stylesheets/components/design_management/design_list_item.scss

 .design-list-item {
+  height: 280px;
   text-decoration: none;
 
   .icon-version-status {
@@ -6,4 +7,13 @@
     right: 10px;
     top: 10px;
   }
+
+  .design-event {
+    top: $gl-padding;
+    right: $gl-padding;
+  }
+
+  .card-body {
+    height: 230px;
+  }
 }

ee/app/assets/stylesheets/pages/design_management.scss

-.design-detail {
-  background-color: rgba($black, 0.9);
-
-  .with-performance-bar & {
-    top: 35px;
-  }
-}
-
-.design-list-item {
-  height: 280px;
-
-  .card-body {
-    height: 230px;
-  }
-}