Ability to convert from Generic Result to Non-Generic Result

[mlienau]

[paulirwin]

Some additional context: this is needed even though Result<T> inherits from Result because the various Result<T> subtypes do not inherit from their non-generic counterparts (like ValidationFailedResult; cannot multi-inherit), so pattern matching on the result fails if you try to return a Result<T>-derived instance from a command/query handler that returns Result.