Add deconstruct to Option/Maybe to support eg (hasValue, value) = collection.TryFirst(...)

[DavidArno]

Based on a suggestion from @pkanavos:

1. Add a deconstruct to Option<T> (and Maybe<T> if it doesn't just work through implicit casting):

   public void Deconstruct<T>(out bool hasValue, out T value) => ...

2. Look at possibly adding similar deconstructs to Success<T>, Either<T1, T2> and union types.

[megafinz]

What will value contain if hasValue is false?

[DavidArno]

default(T) would seem the obvious choice. I'd prefer the idea that its undefined, but out parameters have to be set, always, so that isn't an option.

If you think this inherently a bad idea though, I'm open to being convinced to drop it.

[megafinz]

I don't think that's a bad idea, but I feel like it should be consistent with how Option<T>.Value behaves. Right now it's determined to throw an exception if HasValue == false, so maybe Option<T>.Value should return default(T) as well in this case.

[DavidArno]

If I changed Option<T>.Value to return default<T> when there's no value, then that would be a breaking change. So the choices are:

1. Wait until v4 and introduce that breaking change (in reality there need not be a wait, v4 could be the next release, though this would mean creating a major version release though for a minor feature).
2. Add a Option<T>.ValueOrDefault property that behaves this way and leave Option<T>.Value, as is.

[megafinz]

Option<T>.ValueOrDefault seems legit.

[DavidArno]

Added to v3.1