New Check: Unsafe Enum.at in pipeline (Similar to MapGetUnsafePass)

[JohnnyCurran]

What do you want Credo to do?

• Add a check for unsafe Enum.at when it is not given a safe default argument
• We have had several errors caused by Enum.at calls in pipelines which could have been avoided had there been a default argument or caught by Credo

Which existing behaviour would change?

• Add a check that functions similarly to MapGetUnsafePass that would prevent Enum.at calls in pipelines that do not have a default value