RFR: CODETOOLS-7902812: Fields can still be default initialized if class has only static intializers

[Volker Simonis]

`JCStressTestProcessor` processes a jcstress test `X.java` and generates the corresponding `X_jcstress.java` wrapper class. In this class it generates a `jcstress_consume()` method which resets the status of the stress test after every iteration. If the initial `X.java` stress test class only has primitive fields, a default constructor and no instance initializer, it's fields can be simply reset to default values. Otherwise the method allocates a completely new `X` object.

The current check for default initialization of fields makes no distinction between instance and static (i.e. class) initializers and rejects default initialization of fields in the presence of each of them. Fields can however still be default initialized if a class only has static initializers. This saves some allocations and GC-cycles mostly for the VarHandle tests where the VarHandles are commonly initialized in static initializers.

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Commit messages:
 - CODETOOLS-7902812: Fields can still be default initialized if class has only static intializers

Changes: https://git.openjdk.java.net/jcstress/pull/5/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jcstress&pr=5&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7902812
  Stats: 3 lines in 1 file changed: 3 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jcstress/pull/5.diff
  Fetch: git fetch https://git.openjdk.java.net/jcstress pull/5/head:pull/5

PR: https://git.openjdk.java.net/jcstress/pull/5