Allow the Dropdown component (or a variant) to render an optional Button that applies the selected option

[Josh68]

On MCT, we use an A11Y-approved pattern that involves both a Dropdown component and a Button that applies the last selected option. Also approved in this pattern, the Button is disabled when the selected option is the currently applied option (this is an exception to the general rule of not disabling buttons).

The purpose for this pattern is because it's not considered an accessible pattern, or good UX, to have the act of selecting an option update the UI. It is acceptable to update the UI if you provide a button (generally with the label "Change" or "Apply") as the affordance that triggers the UI updates.

As it is, we can place a Button next to the rendered UI of a Dropdown, but it's not ideal, because the Dropdown renders a label, possibly a description, and a select element. Aligning the button with the select could be handled more elegantly if Dropdown (or a variation of it) rendered the two elements directly next to each other (e.g., in a flex container).

Beyond that, it would be nice to have all of the behavior described encapsulated inside the component: The selected option is applied only when the Button is clicked, and the Button is disabled when the selected option is already applied.