[lworld] RFR: 8296423: [lworld] add VarHandle tests for value classes

[Mandy Chung]

Add VarHandle tests for value class.   This fixes a bug in Unsafe::compareAndSet support.   This also cleans up test/jdk/java/lang/invoke/VarHandles tests such that it only extends the tests for value class and primitive class.  The test cases  for accessing fields declared in a value class or a primitive class are covered by tests in test/jdk/valhalla/valuetypes.

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Commit messages:
 - clean up tests
 - Add VarHandle tests for value class and fix issues

Changes: https://git.openjdk.org/valhalla/pull/804/files
 Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=804&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8296423
  Stats: 5103 lines in 35 files changed: 4290 ins; 662 del; 151 mod
  Patch: https://git.openjdk.org/valhalla/pull/804.diff
  Fetch: git fetch https://git.openjdk.org/valhalla pull/804/head:pull/804

PR: https://git.openjdk.org/valhalla/pull/804