[jdk25] RFR: 8360887: (fs) Files.getFileAttributeView returns unusable FileAttributeView if UserDefinedFileAttributeView unavailable (aix)

[Martin Doerr]

Clean backport of [JDK-8360887](https://bugs.openjdk.org/browse/JDK-8360887).

-------------

Commit messages:
 - Backport 0572b6ece7a77d13d23ac0c6d72d4fe5d5f0d944

Changes: https://git.openjdk.org/jdk/pull/26058/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26058&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8360887
  Stats: 22 lines in 2 files changed: 15 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/26058.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26058/head:pull/26058

PR: https://git.openjdk.org/jdk/pull/26058