RFR: 8339167: Remove AbstractPoolEntry.PrimitiveEntry to reduce boxing overheads

[Claes Redestad]

Removing PrimitiveEntry reduces boxing/unboxing and removes a class.

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Commit messages:
 - Revert tag rewrite
 - Remove AbstractPoolEntry.PrimitiveEntry to reduce boxing overheads

Changes: https://git.openjdk.org/jdk/pull/20749/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20749&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339167
  Stats: 127 lines in 2 files changed: 81 ins; 22 del; 24 mod
  Patch: https://git.openjdk.org/jdk/pull/20749.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20749/head:pull/20749

PR: https://git.openjdk.org/jdk/pull/20749