A "SimpleList" widget

### What is the problem or limitation you are having?

We already have a detailedlist. However, some people may not want the secondary line of text.

### Describe the solution you'd like

Either a new widget named SimpleList, or implement an option in DetailedList to do without the second line.

### Describe alternatives you've considered

Do nothing; people can leave secondary blank.

### Additional context

An example of what this looks like would be the list displayed in the "More" tab in OptionContainers in iOS right now.

Start by locating the existing DetailedList widget and the OptionContainers “More” tab implementation on iOS, then compare how secondary text is handled. Clarify with maintainers whether this should be a SimpleList widget or a DetailedList option; done means lists can omit the secondary line and match the requested appearance.

Written by the indexing model from the issue text.