RFR: 8343650: Reuse StringLatin1::putCharsAt and StringUTF16::putCharsAt

[Shaojin Wen]

Reuse the optimized putCharsAt method of StringLatin1 and StringUTF16 in PR #19626 to simplify the code, eliminate boundary checks, and improve performance

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Commit messages:
 - use StringLatin1::putCharsAt and StringUTF16::putCharsAt

Changes: https://git.openjdk.org/jdk/pull/21907/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21907&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8343650
  Stats: 36 lines in 1 file changed: 0 ins; 28 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/21907.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21907/head:pull/21907

PR: https://git.openjdk.org/jdk/pull/21907