RFR: 8343823: (fs) Files.createLink: inconsistent behavior when creating link to symbolic link

[Brian Burkhalter]

Add an API note to `java.nio.file.Files.createLink` to make explicit that the behavior when the target is a symbolic link is unspecified.

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Commit messages:
 - 8343823: (fs) Files.createLink: inconsistent behavior when creating link to symbolic link

Changes: https://git.openjdk.org/jdk/pull/22257/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22257&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8343823
  Stats: 5 lines in 1 file changed: 5 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/22257.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22257/head:pull/22257

PR: https://git.openjdk.org/jdk/pull/22257