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

[Volkan Yazici]

Replaces `os.name` checks in tests with `@requires`. This prevents these tests from being run, and superficial results being generated, on unnecessary platforms.

Note that `os.name` checks are replaced with `os.family` instead.

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Commit messages:
 - Replace in-test `os.name` checks with `@requires`

Changes: https://git.openjdk.org/jdk/pull/24997/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24997&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8355578
  Stats: 72 lines in 6 files changed: 9 ins; 55 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/24997.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24997/head:pull/24997

PR: https://git.openjdk.org/jdk/pull/24997