RFR: 8329994: Zap alignment padding bits for ArrayOops in non-release builds

[Axel Boldt-Christmas]

In a similar vein to [JDK-8325870](https://bugs.openjdk.org/browse/JDK-8325870). Zap the any alignment padding that may exist between the header and the payload.

Currently this padding only occurs when disabling `UseCompressedClassPointers`. But becomes more relevant with [JDK-8294992](https://bugs.openjdk.org/browse/JDK-8294992).

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Commit messages:
 - 8329994: Zap alignment padding bits for ArrayOops in non-release builds

Changes: https://git.openjdk.org/jdk/pull/18714/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18714&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8329994
  Stats: 18 lines in 3 files changed: 18 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/18714.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18714/head:pull/18714

PR: https://git.openjdk.org/jdk/pull/18714