rename `Result` variants `Ok`/`Err` to `Pass`/`Fail`

[soc]

I was never too happy with the existing naming approaches for the Result type:

Success/Failure

• pro: both names have the same length, like Option's Some/None
• con: quite long, concern that people may use Option over Result

Ok/Err

• pro: short
• con: names don't have the same length, leading to inconsistent indentation when pattern matching
• con: Err is not a word

---

The new naming ticks all the boxes:

Pass/Fail

• pro: both names have the same length
• pro: same length as Some/None
• pro: real words

It's a minor thing, but it's nice to have found a good design even where it doesn't matter that much!

The only concern I have is that I might find a type in a testing-related context where Pass/Fail would fit even better!

[soc]

After the implementation of https://github.com/core-lang/core/issues/8, Option and Result could actually "share" the good case:

class Some[T](val: T)
module None
enum Option[T] of Some[T], None
enum Result[T, E] of Some[T], ???[E]

This still leaves open the question what to call the non-success variant of Result.

[soc]

Adrian from Coffee Compiler Club mentioned Is and No as a possibility. :-)