Add support for InputGroup contents to ValidatedTextInput #55
Description
For kubev2v/forklift-ui#468, we needed to add a show/hide button attached to the password input fields by wrapping the TextInput in an InputGroup. Because ValidatedTextInput renders its own FormGroup internally, it doesn't give us the ability to customize the JSX around the inner TextInput, so I'm having to duplicate a version of ValidatedTextInput in forklift-ui temporarily.
After this issue is addressed, we should refactor forklift-ui's ValidatedPasswordInput component to use the new functionality, and possibly bring that component in to lib-ui as well.