Formik (the React form library) has released a new major version (currently at 2.1.4) which allows use of React Hooks. We should upgrade our ForemanForm component to take advantage of this.

The TextField component inside ForemanForm uses a "render" prop in the Formik <Field> component, which is now deprecated and was causing me some issues similar to [this](https://stackoverflow.com/questions/47012169/a-component-is-changing-an-uncontrolled-input-of-type-text-to-be-controlled-erro).

Since <ForemanForm> is centralized in a single place, it should be relatively straightforward to do the upgrade.

See https://jaredpalmer.com/formik/docs/migrating-v2