RFR: CODETOOLS-7903216: jcstress: JDK 19 compatibility fixes

[Aleksey Shipilev]

Make sure we are able to build and run with JDK 19. GHA already tests this, and is currently failing.

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/jcstress/pull/115/files
 Webrev: https://webrevs.openjdk.org/?repo=jcstress&pr=115&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903216
  Stats: 10 lines in 1 file changed: 9 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jcstress/pull/115.diff
  Fetch: git fetch https://git.openjdk.org/jcstress pull/115/head:pull/115

PR: https://git.openjdk.org/jcstress/pull/115