RFR: 8333133: Simplify QuickSort::sort [v3]

[Kim Barrett]

> The "idempotent" argument is removed from that function, with associated
> simplifications to the implementation. Callers are updated to remove that
> argument. Callers that were providing a false value are unaffected in their
> behavior.  The 3 callers that were providing a true value to request the
> associated feature are also unaffected (other than by being made faster),
> because the arrays involved don't contain any equivalent pairs.
> 
> There are also some miscellaneous cleanups, including using the swap utility
> and fixing some comments.
> 
> Testing: mach5 tier1-3

Kim Barrett has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:

 - Merge branch 'master' into no-idempotent-quicksort
 - Merge branch 'master' into no-idempotent-quicksort
 - improve find_pivot description
 - remove idempotent

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/19464/files
  - new: https://git.openjdk.org/jdk/pull/19464/files/5cee3b81..07dd7040

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=19464&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19464&range=01-02

  Stats: 73160 lines in 1648 files changed: 45921 ins; 20473 del; 6766 mod
  Patch: https://git.openjdk.org/jdk/pull/19464.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19464/head:pull/19464

PR: https://git.openjdk.org/jdk/pull/19464