RFR: 7903464: JMH: Add virtual threads executor [v2]

[Sergey Kuksenko]

> The list of working threads executors should be expanded with virtual threads executor.
> Added VIRTUAL_TPE which is  "Executors.newFixedThreadPool(maxThreads, virtualThreadFactory)).

Sergey Kuksenko has updated the pull request incrementally with one additional commit since the last revision:

  cleanup code

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Changes:
  - all: https://git.openjdk.org/jmh/pull/102/files
  - new: https://git.openjdk.org/jmh/pull/102/files/7556dbe0..345c696f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jmh&pr=102&range=01
 - incr: https://webrevs.openjdk.org/?repo=jmh&pr=102&range=00-01

  Stats: 14 lines in 2 files changed: 0 ins; 1 del; 13 mod
  Patch: https://git.openjdk.org/jmh/pull/102.diff
  Fetch: git fetch https://git.openjdk.org/jmh.git pull/102/head:pull/102

PR: https://git.openjdk.org/jmh/pull/102