[crac] RFR: 8347514: Checkpoint fails with CheckUnhandledOops

[Timofei Pushkin]

Uses `new_args` in `crac::checkpoint()` via a handle to ensure it is not dangling on potential safepoints.

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Commit messages:
 - Checkpoint fails with CheckUnhandledOops

Changes: https://git.openjdk.org/crac/pull/181/files
  Webrev: https://webrevs.openjdk.org/?repo=crac&pr=181&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8347514
  Stats: 6 lines in 1 file changed: 3 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/crac/pull/181.diff
  Fetch: git fetch https://git.openjdk.org/crac.git pull/181/head:pull/181

PR: https://git.openjdk.org/crac/pull/181