RFR: 8290894: Reduce runtime of vm.lang microbenchmarks [v2]

[Eric Caspole]

> Adds fork and iterations controls. This reduces the runtime from 4h26m to about 21m and still seems stable enough for weekly testing.

Eric Caspole has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:

 - Merge branch 'master' into JDK-8290894
 - 8290894: Reduce runtime of vm.lang microbenchmarks

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/9619/files
  - new: https://git.openjdk.org/jdk/pull/9619/files/373da451..08449dd5

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9619&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9619&range=00-01

  Stats: 2646 lines in 96 files changed: 1352 ins; 1038 del; 256 mod
  Patch: https://git.openjdk.org/jdk/pull/9619.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9619/head:pull/9619

PR: https://git.openjdk.org/jdk/pull/9619