[crac] RFR: Improved open file descriptors tracking [v9]

[Radim Vansa]

> Tracks `java.io.FileDescriptor` instances as CRaC resource; before checkpoint these are reported and if not allow-listed (e.g. as opened as standard descriptors) an exception is thrown. Further investigation can use system property `jdk.crac.collect-fd-stacktraces=true` to record origin of those file descriptors.
> File descriptors claimed in Java code are passed to native; native code checks all open file descriptors and reports error if there's an unexpected FD that is not included in the list passed previously.

Radim Vansa has updated the pull request incrementally with one additional commit since the last revision:

  Provide more information for file descriptors

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Changes:
  - all: https://git.openjdk.org/crac/pull/43/files
  - new: https://git.openjdk.org/crac/pull/43/files/8b51d32a..8cba86df

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=crac&pr=43&range=08
 - incr: https://webrevs.openjdk.org/?repo=crac&pr=43&range=07-08

  Stats: 360 lines in 7 files changed: 281 ins; 72 del; 7 mod
  Patch: https://git.openjdk.org/crac/pull/43.diff
  Fetch: git fetch https://git.openjdk.org/crac.git pull/43/head:pull/43

PR: https://git.openjdk.org/crac/pull/43