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

[Laurent Bourgès]

* Optimized mixed insertion sort
    * Optimized insertion sort
    * Optimized Radix sort
    * Updated microbenchmark

I am going on previous PR by Vladimir Yaroslavskyi: https://github.com/openjdk/jdk/pull/3938

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

Commit messages:
 - JDK-8266431: Dual-Pivot Quicksort improvements (Radix sort)

Changes: https://git.openjdk.org/jdk/pull/13568/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13568&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8266431
  Stats: 4022 lines in 4 files changed: 1747 ins; 1272 del; 1003 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