RFR: 8154364: Files.isSameFile() throws NoSuchFileException with broken symbolic links

[Brian Burkhalter]

This request proposes to broaden the definition of which paths are considered to be the same by `java.nio.file.Files.isSameFile()`. A new test is added to cover many comparisons.

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Commit messages:
 - 8154364: Files.isSameFile() throws NoSuchFileException with broken symbolic links

Changes: https://git.openjdk.org/jdk/pull/26736/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26736&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8154364
  Stats: 593 lines in 4 files changed: 533 ins; 24 del; 36 mod
  Patch: https://git.openjdk.org/jdk/pull/26736.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26736/head:pull/26736

PR: https://git.openjdk.org/jdk/pull/26736