RFR: 8290531: Loom: Parallelize a few tests more deeply [v2]

[Aleksey Shipilev]

> Some of the newly added Loom tests are long-running, and thus they delay the completion of otherwise very parallel tier1/jdk_loom. We can parallelize them a bit better to avoid these testing stalls. 
> 
> Improvements on Linux x86_64, TR 3970X, `jdk_loom hotspot_loom`:
> 
> 
> # release before
> real 4m41.424s
> user 24m18.064s
> sys 1m16.440s
> 
> # release after
> real 2m47.769s   ; -40%
> user 23m44.622s
> sys 1m15.240s
> 
> 
> # fastdebug before
> real 5m38.078s
> user 67m23.516s
> sys 1m56.446s
> 
> # fastdebug after
> real 4m9.249s    ; -26%
> user 67m21.940s
> sys 1m57.625s

Aleksey Shipilev 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 four additional commits since the last revision:

 - Review comments
 - Merge branch 'master' into JDK-8290531-loom-tests-parallel
 - More fixes
 - Fix

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/9554/files
  - new: https://git.openjdk.org/jdk/pull/9554/files/3f9bf337..e87544f2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9554&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9554&range=00-01

  Stats: 16874 lines in 645 files changed: 10175 ins; 4817 del; 1882 mod
  Patch: https://git.openjdk.org/jdk/pull/9554.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9554/head:pull/9554

PR: https://git.openjdk.org/jdk/pull/9554