RFR: 8339290: Optimize ClassFile Utf8EntryImpl#writeTo [v20]

[Shaojin Wen]

> Use fast path for ascii characters 1 to 127 to improve the performance of writing Utf8Entry to BufferWriter.

Shaojin Wen has updated the pull request incrementally with one additional commit since the last revision:

  from @cl4es 's suggestion

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Changes:
  - all: https://git.openjdk.org/jdk/pull/20772/files
  - new: https://git.openjdk.org/jdk/pull/20772/files/7d1b2631..c257cf36

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20772&range=19
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20772&range=18-19

  Stats: 2 lines in 1 file changed: 1 ins; 1 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/20772.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20772/head:pull/20772

PR: https://git.openjdk.org/jdk/pull/20772