RFR: Separate young and old regions in age census at end of each GC [v2]

[Kelvin Nilsen]

> We are primarily interested in the young-gen aged regions.  It is confusing for the log report to add the live data pertaining to old-gen regions which happen to have age > 0.

Kelvin Nilsen has updated the pull request incrementally with one additional commit since the last revision:

  Add separate report for old region age table

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Changes:
  - all: https://git.openjdk.org/shenandoah/pull/230/files
  - new: https://git.openjdk.org/shenandoah/pull/230/files/379874e5..eb727d9d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=shenandoah&pr=230&range=01
 - incr: https://webrevs.openjdk.org/?repo=shenandoah&pr=230&range=00-01

  Stats: 12 lines in 1 file changed: 7 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/shenandoah/pull/230.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah.git pull/230/head:pull/230

PR: https://git.openjdk.org/shenandoah/pull/230