RFR: 7903420: jcstress: Trim down the large array tests

[Aleksey Shipilev]

These frequently time out on slower development boards.

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/jcstress/pull/130/files
 Webrev: https://webrevs.openjdk.org/?repo=jcstress&pr=130&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903420
  Stats: 47 lines in 9 files changed: 0 ins; 0 del; 47 mod
  Patch: https://git.openjdk.org/jcstress/pull/130.diff
  Fetch: git fetch https://git.openjdk.org/jcstress pull/130/head:pull/130

PR: https://git.openjdk.org/jcstress/pull/130