RFR: 8316587: Use ArraysSupport.vectorizedHashCode in Utf8EntryImpl

[Chen Liang]

Like #12077, this uses JDK's internal utilities to speed up ASCII reading in Class files, where most identifiers, from conventions to attribute names, are ASCII. See the JBS issue for more in-depth explanations.

Before: (Master)

Benchmark                         Mode  Cnt    Score   Error  Units
ReadMetadata.jdkReadMemberNames  thrpt    4  167.623 ± 8.522  ops/s


After: (This patch, first revision)

Benchmark                         Mode  Cnt    Score   Error  Units
ReadMetadata.jdkReadMemberNames  thrpt    4  175.908 ± 4.766  ops/s

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Commit messages:
 - Use JLA string utilities for utf8 entry reading

Changes: https://git.openjdk.org/jdk/pull/15837/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15837&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8316587
  Stats: 47 lines in 2 files changed: 24 ins; 13 del; 10 mod
  Patch: https://git.openjdk.org/jdk/pull/15837.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15837/head:pull/15837

PR: https://git.openjdk.org/jdk/pull/15837