RFR: 8378119: GenShen: Restore log message about characteristics of promotion efforts

[William Kemper]

Looks like we [lost this](https://github.com/openjdk/jdk/commit/ec059c0e85bc612f430269d9e110dc7ecbdce342#diff-c12167a6c830bdbc58ded4f8ca48faf42af08e5c786ca3d8545bf8abc56fe44cL1094) when [JDK-8365880](https://bugs.openjdk.org/browse/JDK-8365880) was integrated.

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Commit messages:
 - Log promotion summary when cycles complete

Changes: https://git.openjdk.org/jdk/pull/29796/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29796&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8378119
  Stats: 8 lines in 1 file changed: 8 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/29796.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29796/head:pull/29796

PR: https://git.openjdk.org/jdk/pull/29796