RFR: CODETOOLS-7902998: jcstress: Add new ThreadMXBeanAlloc test

[Aleksey Shipilev]

This adds the test to demonstrate the racy behavior of TLAB allocation data:


$ mvn clean install -pl tests-custom
$ java -jar tests-custom/target/jcstress.jar -t ThreadMXBeanAlloc

.......... [OK] o.o.j.t.mxbeans.ThreadMXBeanAlloc

  Results across all configurations:

       RESULT SAMPLES FREQ EXPECT DESCRIPTION
  false, true 2,901 <0.01% Interesting At least one thread experiences delta <0
  true, false 4,232 <0.01% Interesting At least one thread experiences delta <0
   true, true 258,364,451 100.00% Acceptable Delta is >= 0

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

Commit messages:
 - Stylistic cleanups
 - CODETOOLS-7902998: jcstress: Add new ThreadMXBeanAlloc test

Changes: https://git.openjdk.java.net/jcstress/pull/90/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jcstress&pr=90&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7902998
  Stats: 72 lines in 1 file changed: 72 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jcstress/pull/90.diff
  Fetch: git fetch https://git.openjdk.java.net/jcstress pull/90/head:pull/90

PR: https://git.openjdk.java.net/jcstress/pull/90