[jdk21u-dev] RFR: 8355578: [java.net] Use @requires tag instead of exiting based on "os.name" property value

[Goetz Lindenmaier]

I backport this for parity with 21.0.9-oracle

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Commit messages:
 - Backport 60a4594b9f9acd82ef3ff22fc6a2df238dd981b9

Changes: https://git.openjdk.org/jdk21u-dev/pull/1978/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1978&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8355578
  Stats: 74 lines in 6 files changed: 11 ins; 55 del; 8 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1978.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1978/head:pull/1978

PR: https://git.openjdk.org/jdk21u-dev/pull/1978