[jdk21u] RFR: 8338696: (fs) BasicFileAttributes.creationTime() falls back to epoch if birth time is unavailable (Linux)

[Severin Gehwolf]

Clean backport to improve compatibility with JDK 21 versions which didn't support birth time. I.e. on those systems now last-modified-time is being returned when the `statx` syscall didn't fill in the birth time (is not supported for this filesystem). Proposing as a critical fix so as to get it into 21.0.5.

CSR for 21-pool and 17-pool is the same as for JDK head, but would need a review before I can submit it. If anyone is willing to review it, I'd appreciate it. Thanks!

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Commit messages:
 - 8338696: (fs) BasicFileAttributes.creationTime() falls back to epoch if birth time is unavailable (Linux)

Changes: https://git.openjdk.org/jdk21u/pull/450/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u&pr=450&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8338696
  Stats: 21 lines in 1 file changed: 12 ins; 0 del; 9 mod
  Patch: https://git.openjdk.org/jdk21u/pull/450.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u.git pull/450/head:pull/450

PR: https://git.openjdk.org/jdk21u/pull/450