This provides a standard menu implementation that we can use any time we

need a menu. It supports dynamically adding items and opening/closing

the menu (with and without animation).
All accessibility needs are covered by this class. It handles setting

the appropriate ARIA roles on the menu, menu items, and the controlling

element that opens the menu. It also handles full keyboard navigation,

allowing the menu to be interacted with entirely by keyboard.
Unit tests cover all the rendering options, focus management, ARIA

attributes/states, and keyboard accessibility available in this

component.

Unit tests passed.
Used this with an upcoming change that updates RB.SplitButtonView to

use RB.MenuView.