RFR: 8377035: [s390x] Disable JSR166 test cases which uses virtual threads [v2]

[Harshit470250]

> ReentrantReadWriteLock20Test.java is failing on s390 due to virtual threads which are not yet implemented on s390. 
> SynchronousQueue20Test.java also uses virtual thread so I am also disabling it.

Harshit470250 has updated the pull request incrementally with one additional commit since the last revision:

  change to use Platform.isS390

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/29555/files
  - new: https://git.openjdk.org/jdk/pull/29555/files/d25dd14d..746240a7

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29555&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29555&range=00-01

  Stats: 6 lines in 1 file changed: 5 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/29555.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29555/head:pull/29555

PR: https://git.openjdk.org/jdk/pull/29555