<i18n dev> RFR: 8338409: Use record to simplify code

[Shaojin Wen]

j.u.Formatter$FixedString can be refactored to simplify the code using Record

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Commit messages:
 - Update src/java.base/share/classes/java/util/Formatter.java
 - use record to simplify code

Changes: https://git.openjdk.org/jdk/pull/20443/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20443&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8338409
  Stats: 9 lines in 1 file changed: 0 ins; 8 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/20443.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20443/head:pull/20443

PR: https://git.openjdk.org/jdk/pull/20443