chore(list): ensure the menu is always on the far right

Sometimes, `primaryComponent`s in list items need to get
`order: 2;` to be placed after the text. But since the default `order`
of all lit item children is `0`, we need to push the menu to the far right
by giving it a bigger order number. Also, by making this into a variable
we can handle other edge-cases in consuming components.

src/components/list/list.scss

@@ -123,6 +123,7 @@ $list-mdc-list-item: 0;
         // the action menu on the right side a list item
         line-height: 100%;
         margin-right: -0.5rem;
+        order: var(--limel-list-meta-order, 3);
     }
 
     .mdc-deprecated-list-item__graphic {