RFR: CODETOOLS-7902916: jcstress: Pass a limited subset of TestConfig to the forked VMs

[Aleksey Shipilev]

Current TestConfig is serialized and passed in full to the forked VMs. It carries a lot of baggage that forked VM does not really care about. We can instead pass a very limited subset of it. It also opens the way to use the small non-Java-Serialization format later.

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

Commit messages:
 - Fixes
 - More improvements
 - More improvements
 - Split out ForkedTestConfig

Changes: https://git.openjdk.java.net/jcstress/pull/44/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jcstress&pr=44&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7902916
  Stats: 214 lines in 12 files changed: 113 ins; 70 del; 31 mod
  Patch: https://git.openjdk.java.net/jcstress/pull/44.diff
  Fetch: git fetch https://git.openjdk.java.net/jcstress pull/44/head:pull/44

PR: https://git.openjdk.java.net/jcstress/pull/44