RFR: 7902989: jcstress: Add samples for high-level race conditions [v4]

[Michael Mirwaldt]

> I have created two more samples:
> 
> - one sample for read-modify-write-sequences
> - one sample for check-then-react-sequences

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

  using an arbiter now in RaceCondition_01_ReadModifyWriteSequence

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

Changes:
  - all: https://git.openjdk.java.net/jcstress/pull/88/files
  - new: https://git.openjdk.java.net/jcstress/pull/88/files/38b805b0..23ab224a

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jcstress&pr=88&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jcstress&pr=88&range=02-03

  Stats: 10 lines in 1 file changed: 5 ins; 4 del; 1 mod
  Patch: https://git.openjdk.java.net/jcstress/pull/88.diff
  Fetch: git fetch https://git.openjdk.java.net/jcstress pull/88/head:pull/88

PR: https://git.openjdk.java.net/jcstress/pull/88