function getDefaultValue(props, propKey) {
  return getDefaultValueCommon(props, propKey, defaultStateValues)
}
Returns the default value for a state key in the following order:
1. controlled prop, 2. default prop, 3. default value from Downshift.

@param {Object} props Props passed to the hook.
@param {string} propKey Props key to generate the value for.
@returns {any} The initial value for that prop.