RFR: 8338546: Speed up ConstantPoolBuilder::classEntry(ClassDesc)

[Chen Liang]

Speed up `ConstantPoolBuilder::classEntry(ClassDesc)` by going through `ClassDesc` comparison and reusing descriptor hash to calculate internal name hash if possible. No suitable device to run benchmarks so need to find something to run the new benchmark to ensure things work as intended.

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Commit messages:
 - Fix microbenchmark
 - Improve jmh
 - 8338546: Speed up ConstantPoolBuilder::classEntry(ClassDesc)

Changes: https://git.openjdk.org/jdk/pull/20667/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20667&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8338546
  Stats: 499 lines in 7 files changed: 498 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/20667.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20667/head:pull/20667

PR: https://git.openjdk.org/jdk/pull/20667