RFR: 8332826: Make hashCode methods in ArraysSupport friendlier [v2]

[Pavel Rappo]

> Please review this PR, which supersedes a now withdrawn https://github.com/openjdk/jdk/pull/14831.
> 
> This PR replaces `ArraysSupport.vectorizedHashCode` with a set of more user-friendly methods. Here's a summary:
> 
> - Made the operand constants (i.e. `T_BOOLEAN` and friends) and the `vectorizedHashCode` method private
> 
> - Made the `vectorizedHashCode` method private, but didn't rename it. Renaming would dramatically increase this PR review cost, because that method's name is used by a lot of VM code. On a bright side, since the method is now private, it's no longer callable by clients of `ArraysSupport`, thus a problem of an inaccurate name is less severe.
> 
> - Made the `ArraysSupport.utf16HashCode` method private
> 
> - Moved tiny cases (i.e. 0, 1, 2) to `ArraysSupport`

Pavel Rappo has updated the pull request incrementally with one additional commit since the last revision:

  Fix incorrect utf16 hashCode adaptation

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/19414/files
  - new: https://git.openjdk.org/jdk/pull/19414/files/4ed451d6..adc7557d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=19414&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19414&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/19414.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19414/head:pull/19414

PR: https://git.openjdk.org/jdk/pull/19414