RFR: 8361726: Shenandoah: More detailed evacuation instrumentation [v4]

[William Kemper]

> Shenandoah has `not product` instrumentation to track evacuation performance. This change introduces more detail by categorizing each evacuation as young, old or promotion.

William Kemper has updated the pull request incrementally with one additional commit since the last revision:

  Change wording in commment

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Changes:
  - all: https://git.openjdk.org/jdk/pull/26222/files
  - new: https://git.openjdk.org/jdk/pull/26222/files/23a86e36..cd69cd92

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26222&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26222&range=02-03

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/26222.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26222/head:pull/26222

PR: https://git.openjdk.org/jdk/pull/26222