[crac] RFR: 8370888: [CRaC] Use better source of random for UUID generation in checkpoint path

[Radim Vansa]

When `-XX:CRaCCheckpointTo` contains the `%u` placeholder to generate random UUID, it should use a different source than `os::random()` which provides not-seeded, deterministic values.

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Commit messages:
 - 8370888: [CRaC] Use better source of random for UUID generation in checkpoint path

Changes: https://git.openjdk.org/crac/pull/271/files
  Webrev: https://webrevs.openjdk.org/?repo=crac&pr=271&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8370888
  Stats: 64 lines in 6 files changed: 53 ins; 2 del; 9 mod
  Patch: https://git.openjdk.org/crac/pull/271.diff
  Fetch: git fetch https://git.openjdk.org/crac.git pull/271/head:pull/271

PR: https://git.openjdk.org/crac/pull/271