RFR: 8367450: Shenandoah: Log the composition of the collection set

[William Kemper]

Reuse the same log message from GenShen which details the composition of the live data to be evacuated. In the non-generational modes, all regions are considered young and nothing will be promoted (or old).

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Commit messages:
 - Log the composition of live data within the collection set

Changes: https://git.openjdk.org/jdk/pull/27235/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27235&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8367450
  Stats: 118 lines in 5 files changed: 36 ins; 55 del; 27 mod
  Patch: https://git.openjdk.org/jdk/pull/27235.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27235/head:pull/27235

PR: https://git.openjdk.org/jdk/pull/27235