Improve Result and exception handling ergonomics

[Jeehut (Cihat Gündüz)]

@pronebird I just wrote a pitch very much related to this thread, please see here:

If/guard-let-catch for conveniently accessing both Result type cases

Motivation A few weeks ago, I had asked on Twitter if developers prefer error handling in Swift by using throws vs. returning Result. Of the 102 votes, 45% voted for "I prefer Result", which is 40% more than the 32% who voted for "I prefer throws" (source). While this small survey isn't representative by any means, it still proves that there's clearly high interest in using Result for error handling (and not only for closure return types), even if that means we have to build nested error types…