Change icon on MenuButton

[ArakTaiRoth]

Info

Requested by Qing An

Right now, our MenuButton component has only the option for a changing trailing chevron icon (down if closed, up if open). It's been requested to be able to remove that trailing icon, and be able to add their own leading icon.

Acceptance Criteria:

1. The trailing icon should be changeable (as well as made null) and a leading icon should be added.