RFR: 7903422: JMH: Add round-trip benchmarks to core tests

[Aleksey Shipilev]

For some systems, it is instrumental to understand the latency figures between different CPU threads.

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/jmh/pull/94/files
 Webrev: https://webrevs.openjdk.org/?repo=jmh&pr=94&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903422
  Stats: 467 lines in 6 files changed: 466 ins; 1 del; 0 mod
  Patch: https://git.openjdk.org/jmh/pull/94.diff
  Fetch: git fetch https://git.openjdk.org/jmh pull/94/head:pull/94

PR: https://git.openjdk.org/jmh/pull/94