RFR: JDK-8266431: Dual-Pivot Quicksort improvements (Radix sort) [v11]

[Laurent Bourgès]

> * improved  mixed insertion sort (makes whole sorting faster)
> * introduced Radix which sort shows several times boost of performance and has linear complexity instead of n*ln(n)
> * improved merging sort for almost sorted data
> * optimized parallel sorting
> * improved step for pivot candidates and pivot partitioning
> * extended existing tests
> * added benchmarking JMH tests
> * suggested better buffer allocation: if no memory, it is switched to in-place sorting with no OutOfMemoryError, threshold is 1/16th heap
> 
> I am going on previous PR by Vladimir Yaroslavskyi: https://github.com/openjdk/jdk/pull/3938

Laurent Bourgès has updated the pull request incrementally with one additional commit since the last revision:

  add @SuppressWarnings (serial)

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Changes:
  - all: https://git.openjdk.org/jdk/pull/13568/files
  - new: https://git.openjdk.org/jdk/pull/13568/files/13b1b1e9..4744a260

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13568&range=10
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13568&range=09-10

  Stats: 2 lines in 1 file changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/13568.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13568/head:pull/13568

PR: https://git.openjdk.org/jdk/pull/13568