RFR: 7903641: JMH: Rework samples to avoid excess double and volatile cases

[Aleksey Shipilev]

Generally, those samples need a bit of touchup. We used to do doubles there, because the relative overhead for double multiplication showed up against the blackholes overhead. Now that we are using compiler blackholes nearly everywhere, we can redo these in simple ints.

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Commit messages:
 - Fixes

Changes: https://git.openjdk.org/jmh/pull/145/files
  Webrev: https://webrevs.openjdk.org/?repo=jmh&pr=145&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903641
  Stats: 84 lines in 13 files changed: 17 ins; 10 del; 57 mod
  Patch: https://git.openjdk.org/jmh/pull/145.diff
  Fetch: git fetch https://git.openjdk.org/jmh.git pull/145/head:pull/145

PR: https://git.openjdk.org/jmh/pull/145