RFR: 8339342: FieldAllocationCount is mostly unused

[Coleen Phillimore]

The only use for this code except for setting static_oop_field_count was for field allocation code before the FieldLayoutBuilder code was introduced, and continues to be unused for the valhalla field layout code.  Removed it.
Tested with tier1 on linux, windows and macosx platforms.

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Commit messages:
 - 8339342: FieldAllocationCount is mostly unused

Changes: https://git.openjdk.org/jdk/pull/20850/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20850&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339342
  Stats: 108 lines in 2 files changed: 4 ins; 101 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/20850.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20850/head:pull/20850

PR: https://git.openjdk.org/jdk/pull/20850