Add indicators to all drilldown menu items in browse view

[jameskoster]

Part of #36667

With #47777 merged, clicking a template or template part in browse view will expose a subsequent panel in the drilldown navigation:

At the root level the menu items indicate this behavior by displaying a chevron:

We should apply this convention to all menu items in browse view so that users are able to understand upfront whether a menu item will expose a new panel or have a different behavior.

[richtabor]

We should apply this convention to all menu items in browse view so that users are able to understand upfront whether a menu item will expose a new panel or have a different behavior.

I think so too.

[tomdevisser]

+1

[priethor]

Should we consolidate this issue in #48591? If I understand correctly, that issue covers this and more cases, right?