UI ember engines (#6718)

Adds replication engine and core in-repo addon

ui/lib/core/addon/components/layout-loading.js

@@ -0,0 +1,17 @@
+import Component from '@ember/component';
+import layout from '../templates/components/layout-loading';
+
+/**
+ * @module LayoutLoading
+ * `LayoutLoading` displays the `VaultLogoSpinner` component in a centered full-page layout.
+ *
+ * @example
+ * ```js
+ * <LayoutLoading />
+ * ```
+ */
+
+export default Component.extend({
+  layout,
+  tagName: '',
+});