Handle creates a black-box when Submarine escapes rescue

[morgen-peschke]

Code using Handle.allow has to be very careful that none of the code it calls inside of it uses ApplicativeError or MonadError to modify thrown exceptions between when it is created using Raise and when Handle catches and unwraps the Submarine.

If this does happen to happen, the resulting error does not contain any information about the enclosed exception (it's toString is "cats.mtl.Handle$Submarine"), making debugging quite difficult.

Can Submarine be updated to include the wrapped error as it's cause or have some other change so that it'll show in the toString output?