RFR: 8329998: Remove double initialization for parts of small TypeArrays in ZObjArrayAllocator [v2]

[Axel Boldt-Christmas]

> [JDK-8139457](https://bugs.openjdk.org/browse/JDK-8139457) introduced non-word aligned payloads for TypeArrays. This required adaptation in `ZObjArrayAllocator` segmented array allocator. But the implementation does this adaptation even when the size is small enough and dispatches the allocation to `ObjArrayAllocator`, which already handles clearing this memory.
> 
> Instead move the initialization of any unaligned payload start to after the segmented allocation decision.

Axel Boldt-Christmas has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:

 - Merge remote-tracking branch 'upstream_jdk/master' into JDK-8329998
 - 8329998: Remove double initialization for parts of small TypeArrays in ZObjArrayAllocator

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/18721/files
  - new: https://git.openjdk.org/jdk/pull/18721/files/5d055a3d..9c042651

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18721&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18721&range=00-01

  Stats: 127146 lines in 3211 files changed: 60830 ins; 49455 del; 16861 mod
  Patch: https://git.openjdk.org/jdk/pull/18721.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18721/head:pull/18721

PR: https://git.openjdk.org/jdk/pull/18721