RFR: 7903909: JMH: Further generated code touchups

[Aleksey Shipilev]

There are a few leftovers in generated code that we can tune up. Mostly formatting, but some final modifiers are missing, and some other code could be denser.

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/jmh/pull/144/files
  Webrev: https://webrevs.openjdk.org/?repo=jmh&pr=144&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903909
  Stats: 43 lines in 2 files changed: 15 ins; 25 del; 3 mod
  Patch: https://git.openjdk.org/jmh/pull/144.diff
  Fetch: git fetch https://git.openjdk.org/jmh.git pull/144/head:pull/144

PR: https://git.openjdk.org/jmh/pull/144