[Chapel Merge] Put the minlen condition back in quicksort

Branch: refs/heads/main
Revision: f29f270
Author: mppf
Log Message:

Merge pull request #17279 from mppf/quicksort-minlen

Put the minlen condition back in quicksort

It was accidentally removed in PR #15239. Putting it back caused problems
with some mason search testing, but that was because the code sorting
the results for mason search assumed that the sort was stable. It is
not, so this PR updates that mason search implementation to work with
unstable sort and the sort documentation to make it clear that it is not
a stable sort.

Reviewed by @arezaii - thanks!