[jdk23u] RFR: 8339803: Acknowledge case insensitive unambiguous keywords in tzdata files

[Johny Jose]

Clean backport of https://git.openjdk.org/jdk/commit/35a94b769761bd923fe6db03be672f05c1a74c38

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Commit messages:
 - Backport 35a94b769761bd923fe6db03be672f05c1a74c38

Changes: https://git.openjdk.org/jdk23u/pull/162/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk23u&pr=162&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339803
  Stats: 41 lines in 4 files changed: 7 ins; 4 del; 30 mod
  Patch: https://git.openjdk.org/jdk23u/pull/162.diff
  Fetch: git fetch https://git.openjdk.org/jdk23u.git pull/162/head:pull/162

PR: https://git.openjdk.org/jdk23u/pull/162