RFR: 8339290: Optimize ClassFile Utf8EntryImpl#writeTo [v12]

[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 two additional commits since the last revision:

 - improve benchmark, from @liach & @cl4es
 - remove 256

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Changes:
  - all: https://git.openjdk.org/jdk/pull/20772/files
  - new: https://git.openjdk.org/jdk/pull/20772/files/ce6c71e2..77df66f4

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20772&range=11
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20772&range=10-11

  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 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