CiString support

[matt-beanland]

Add Ash.CiString implementation using comparable value on actual first.

[matt-beanland]

defoutstanding expected :: Ash.CiString, actual :: Any do
  Outstanding.outstanding(
    Ash.CiString.to_comparable_string(expected),
    case actual do
      %Ash.CiString{} -> Ash.CiString.to_comparable_string(actual)
      _ -> actual
    end
  )
end