RFR: CODETOOLS-7903004: JMH: Compiler Blackholes auto-detection [v3]

[Aleksey Shipilev]

> This is another step towards better compiler blackholes support. This time, we can enable JMH to auto-detect the support and enable it, if JVM supports it.

Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:

  Disallow selecting compiler blackholes when they are not available

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Changes:
  - all: https://git.openjdk.java.net/jmh/pull/48/files
  - new: https://git.openjdk.java.net/jmh/pull/48/files/920aa051..f27e2a06

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jmh&pr=48&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jmh&pr=48&range=01-02

  Stats: 11 lines in 1 file changed: 9 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jmh/pull/48.diff
  Fetch: git fetch https://git.openjdk.java.net/jmh pull/48/head:pull/48

PR: https://git.openjdk.java.net/jmh/pull/48