Fix #11236:

- Changed side-menu.phtml to have naming in line with the naming in home.phtml. Component was the name in < Magento 2.2
- Updated the less files to reflect these changes and switched the icons in the menu
- Updated compiled setup.css file

Author: dverkade

app/design/adminhtml/Magento/backend/web/app/updater/styles/less/components/_menu.less

@@ -56,15 +56,16 @@
         }
     }
 
-    .item-component {
+    .item-component,
+    .item-extension {
         > a {
             &:before {
                 content: @icon-lego__content;
             }
         }
     }
 
-    .item-extension {
+    .item-module {
         > a {
             &:before {
                 content: @icon-module__content;

setup/pub/styles/setup.css

@@ -39,7 +39,7 @@
                 <span>Extension Manager</span>
             </a>
         </li>
-        <li class="item-component level-0"   ng-class="{_active: $state.current.type === 'module'}">
+        <li class="item-module level-0"   ng-class="{_active: $state.current.type === 'module'}">
             <a href="" ui-sref="root.module">
                 <span>Module Manager</span>
             </a>