Canvas: Refactor classes into functional react components

Many classes inside Canvas ought to be represented as functional React components. Look for classes with a `renderComponent` method to start. When Ash took care of #113808, it became clear that the reason those classes had render methods was because they were awkward, stateful classes which exist outside React's purview. We ought to avoid trying to be more clever than React and just write those components as React components to take advantage of any optimizations React can offer us in terms of managing that state.