[code-reflection] Integrated: HATVectorPhase cleanup/refactoring

[Gary Frost]

Some major refactoring of HATVectorPhase ....

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Commit messages:
 - HATVectorPhase cleanup/refactoring

Changes: https://git.openjdk.org/babylon/pull/853/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=853&range=00
  Stats: 454 lines in 6 files changed: 144 ins; 182 del; 128 mod
  Patch: https://git.openjdk.org/babylon/pull/853.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/853/head:pull/853

PR: https://git.openjdk.org/babylon/pull/853