Comparators support partial ordering

[Akirathan]

All ordered and unordered comparators support partial ordering, not only total ordering - by returning Nothing from some methods.

• Refactor Incomparable_Values to a builtin error

Bench results

• Equality.enso:
  • Speedup in Integer, Boolean, and Text
• EqualsBenchmarks:
  • equalsPrimitives speedup by 20%
  • equalsStrings speedup by 21%

[JaroslavTulach]

#5771 suggests to merge compare and equals, get rid of is_ordered and always just call compare. I still think it should be done... at least one day.

[radeusgd]

Looks good, just some suggestions, mostly I think it would be good to slightly expand on a few test cases.

1. Additionally, I'm wondering how the (Hash)Map behaves in presence of incomparable values - I'm not exactly sure now - so I think it would be beneficial to add some tests showing what is the expected behaviour and that we are conscious of it.

My suggestion:

m = Map.from_vector allow_duplicates=True [[Number.nan, 1], [Number.nan, 2], [Number.nan, 3], [0.5, 4]]
m.size == ??? # idk, are the nans merged or not?
m.contains_key Number.nan == ??? # it does contain it but due to incomparable I guess it may not say that?
m.get Number.nan == ??? # as above
m.get 0.5 . should_equal 4

NaN handling to be addressed in a separate issue #5833

2. I think we should add a test for 2 arrays/hashmaps which contain incomparable values and verify what is the result.

For example

a = [Number.nan, 2]
b = [Number.nan, 2]
(a == b) == ???

I guess it is False but let's have a test showing that.

Also - do you think it is correct for this to be False? My initial intuition would be that the incomparability should be 'poisonous' and if any field in an Atom/Array/Map is incomparable, the whole thing should be incomparble as well. Although I remember the discussions about equality some longer time ago where this was not that obvious because it has its own problems. @JaroslavTulach what do you think about this case?

My_Atom.Value Number.nan == My_Atom.Value Number.nan

should this be False or throw Incomparable_Values?

Personally, I'd go for throwing incomparable values, but I'm not attached to this opinion if anyone thinks False is somehow better (although will appreciate some arguments as to why).