RFR: 8316657: Support whitebox testing in microbenchmarks [v2]

[Magnus Ihse Bursie]

> The need to use whitebox-testing (wb.jar) from JMH microbenchmarks has recently arisen.

Magnus Ihse Bursie has updated the pull request incrementally with one additional commit since the last revision:

  Revert change in RunTests

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Changes:
  - all: https://git.openjdk.org/jdk/pull/16996/files
  - new: https://git.openjdk.org/jdk/pull/16996/files/320a911d..9e394618

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16996&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16996&range=00-01

  Stats: 3 lines in 1 file changed: 0 ins; 1 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/16996.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16996/head:pull/16996

PR: https://git.openjdk.org/jdk/pull/16996