[lworld] RFR: 8376461: [lworld] serviceability/jvmti/valhalla/HeapDump/HeapDump.java fails More than 1 instances of 'TestClass' found

[Alex Menkov]

TestClass is a container class which contains a number of value object, main test process and target VM create TestClass object, so the test can compare the object and its representation in the target VM heap dump.
After JDK-8376135 `new TestClass()` may cause unreachable TestClass instance is still in the heap, so it appears in the heap dump too.
The simplest solution is to make TestClass non-value class (actual tested value classes are nested classes of TestClass)

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

Commit messages:
 - fix

Changes: https://git.openjdk.org/valhalla/pull/2109/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=2109&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8376461
  Stats: 2 lines in 2 files changed: 0 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/valhalla/pull/2109.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/2109/head:pull/2109

PR: https://git.openjdk.org/valhalla/pull/2109