RFR: 8367989: Remove InstanceKlass::allocate_objArray

[Coleen Phillimore]

This change removes InstanceKlass::allocate_objArray and has its caller call ObjArrayKlass::allocate_instance directly from oopFactory, like the other array allocations do.  See CR for more information why we should have this change.  I also removed element_klass_addr() and moved element_klass_offset() to be in a more logical place near element_klass() functions.  This upstreams a tiny valhalla diff.
Tested with tier1-4.

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Commit messages:
 - 8367989: Remove InstanceKlass::allocate_objArray

Changes: https://git.openjdk.org/jdk/pull/27372/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27372&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8367989
  Stats: 19 lines in 4 files changed: 3 ins; 14 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/27372.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27372/head:pull/27372

PR: https://git.openjdk.org/jdk/pull/27372