RFR: 8312424: 80% throughput decrease in Arrays.hashCode(Object[]) after JDK-8312164

[Glavo]

The changes to `Arrays.hashCode(Object[])` in JDK-8312164 caused its performance  is reduced by about 80%.

This PR reverts this change.

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Commit messages:
 - Add benchmark
 - Revert changes to Arrays.hashCode(Object[]) in JDK-8312164

Changes: https://git.openjdk.org/jdk/pull/14944/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14944&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8312424
  Stats: 9 lines in 2 files changed: 8 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/14944.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14944/head:pull/14944

PR: https://git.openjdk.org/jdk/pull/14944