[jdk21u-dev] RFR: 8356107: [java.lang] Use @requires tag instead of exiting based on os.name or separatorChar property

[Goetz Lindenmaier]

I backport this for parity with 21.0.11-oracle.

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Commit messages:
 - Backport d1543429ff29ca0d761b8473b3fb8621abcd226d

Changes: https://git.openjdk.org/jdk21u-dev/pull/2591/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=2591&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8356107
  Stats: 82 lines in 4 files changed: 3 ins; 73 del; 6 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/2591.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/2591/head:pull/2591

PR: https://git.openjdk.org/jdk21u-dev/pull/2591