[IMP] web: add className getter in list view

Before this commit, the kanban view has a `className` getter to easily
add a class if needed. The list view only uses the className given in
the props and so className is added in the view.

This commit adds a className getter to be consistent with kanban view
and to allow to easily add a className to a specific case (that is for
an eventual customization).

task-2713538

Part-of: odoo/odoo#98380

addons/web/static/src/views/list/list_controller.js

@@ -279,6 +279,10 @@ export class ListController extends Component {
         }
     }
 
+    get className() {
+        return this.props.className;
+    }
+
     get nbSelected() {
         return this.model.root.selection.length;
     }

addons/web/static/src/views/list/list_controller.xml

@@ -2,7 +2,7 @@
 <templates xml:space="preserve">
 
     <t t-name="web.ListView" owl="1">
-        <div t-att-class="props.className" t-ref="root">
+        <div t-att-class="className" t-ref="root">
             <Layout className="model.useSampleModel ? 'o_view_sample_data' : ''" display="props.display">
                 <t t-set-slot="layout-buttons">
                     <t t-if="env.isSmall and nbSelected">