RFR: 8314139: TEST_BUG: runtime/os/THPsInThreadStackPreventionTest.java could fail on machine with large number of cores [v2]

[Man Cao]

> Hi all, @tstuefe 
> 
> Could anyone review this fix for a test failure that could happen on machines with many cores? This fix caps `-XX:ActiveProcessorCount` to 64, which limits the number of internal threads the JVM creates.
> 
> An alternative is to bump up the `acceptableRSSLimitMB` such as increasing `basicRSSOverheadMB`. However, this approach could be fragile for machines with even more number of cores (e.g. 256 or more).
> 
> -Man

Man Cao has updated the pull request incrementally with one additional commit since the last revision:

  Always set ActiveProcessorCount=2 instead

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/15241/files
  - new: https://git.openjdk.org/jdk/pull/15241/files/28a03d1f..e16760e4

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15241&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15241&range=00-01

  Stats: 10 lines in 1 file changed: 3 ins; 6 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/15241.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15241/head:pull/15241

PR: https://git.openjdk.org/jdk/pull/15241