fix(material-experimental/mdc-list): set a role on MatNavList and MatActionList

make the following changes to align with legacy version of list
 - `MatNavList` apply `role="navigation"`
 - `MatActionList` apply `role="group"`

Author: zarend

src/material-experimental/mdc-list/action-list.ts

@@ -15,6 +15,7 @@ import {MatListBase} from './list-base';
   template: '<ng-content></ng-content>',
   host: {
     'class': 'mat-mdc-action-list mat-mdc-list-base mdc-list',
+    'role': 'group',
   },
   styleUrls: ['list.css'],
   encapsulation: ViewEncapsulation.None,

src/material-experimental/mdc-list/nav-list.ts

@@ -15,6 +15,7 @@ import {MatListBase} from './list-base';
   template: '<ng-content></ng-content>',
   host: {
     'class': 'mat-mdc-nav-list mat-mdc-list-base mdc-list',
+    'role': 'navigation',
   },
   styleUrls: ['list.css'],
   encapsulation: ViewEncapsulation.None,