RFR: 8341485: GenShen: Make evac tracker a non-product feature and confine it to generational mode

[William Kemper]

Not clean.

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Commit messages:
 - 8341485: GenShen: Make evac tracker a non-product feature and confine it to generational mode

Changes: https://git.openjdk.org/shenandoah-jdk21u/pull/117/files
  Webrev: https://webrevs.openjdk.org/?repo=shenandoah-jdk21u&pr=117&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8341485
  Stats: 95 lines in 10 files changed: 34 ins; 32 del; 29 mod
  Patch: https://git.openjdk.org/shenandoah-jdk21u/pull/117.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah-jdk21u.git pull/117/head:pull/117

PR: https://git.openjdk.org/shenandoah-jdk21u/pull/117