RFR: 7903902: JMH: Optimize state overrides for stateless objects

[Aleksey Shipilev]

More investigation for [JDK-8345302](https://bugs.openjdk.org/browse/JDK-8345302) shows we do not need to generate state object overrides if state object does not need any additional fluff. This most prominent for Thread state objects.

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/jmh/pull/141/files
  Webrev: https://webrevs.openjdk.org/?repo=jmh&pr=141&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903902
  Stats: 29 lines in 1 file changed: 14 ins; 15 del; 0 mod
  Patch: https://git.openjdk.org/jmh/pull/141.diff
  Fetch: git fetch https://git.openjdk.org/jmh.git pull/141/head:pull/141

PR: https://git.openjdk.org/jmh/pull/141