Rename default and reverse comparators in the sort module

[jabraham17]

This issue captures implementation information for decision made in https://github.com/chapel-lang/chapel/issues/24857

We are renaming the default comparators and removing the associated globals.

Tasks

• [x] Remove const defaultComarator ..., replacement is new defaultComparator()
• [x] Remove const reverseComarator ..., replacement is new reverseDefaultComparator()
• [ ] Rename DefaultComparator to defaultComparator
• [ ] Rename ReverseComparator to reverseComparator
• [x] ~Add type reverseDefaultComparator = reverseComparator(defaultComparator);~
• Add enum keyPartStatus with the following enum members
  • [x] returned
  • [x] pre
  • [x] post
• [x] Rename defaultComparator.compare(a, b) to defaultComparator.compare(x, y: x.type)
• [x] Rename reverseComparator.compare(a, b) to reverseComparator.compare(x, y: x.type)
• [x] Rename TwoArrayDistSortPerBucketTaskStartComparator.key(arg ... to TwoArrayDistSortPerBucketTaskStartComparator.key(elt ...
  • this is an internal implementation detail and will not require a deprecation
• [x] Convert all keyPart methods to the new style
  • proc keyPart(elt, i: int): (keyPartStatus, integral)