RFR: 8305716: Enhancements for printing age tables

Thu Apr 6 18:26:03 UTC 2023

In order to reduce the number of changes for the upcoming PR for the generational mode for Shenandoah we are opening separate PRs for the changes in common code. Shenandoah will be using this `AgeTable` class. There are two changes here:
* `AgeTables` created with global=false will no longer SEGV when printing
* A method was added to allow the `AgeTable` to print to an existing output stream

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Commit messages:
 - Enhancements for printing the age table

Changes: https://git.openjdk.org/jdk/pull/13377/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13377&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8305716
  Stats: 46 lines in 2 files changed: 22 ins; 15 del; 9 mod
  Patch: https://git.openjdk.org/jdk/pull/13377.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13377/head:pull/13377

PR: https://git.openjdk.org/jdk/pull/13377