RFR: 8339651: ShenandoahPacer::setup_for_mark, ShenandoahPacer::setup_for_updaterefs and ShenandoahPacer::setup_for_evac runtime error: division by zero

[William Kemper]

Avoid divide by zero error when there is no memory available.

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Commit messages:
 - Fix 32bit and windows builds
 - Avoid divide-by-zero error

Changes: https://git.openjdk.org/jdk/pull/21432/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21432&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339651
  Stats: 3 lines in 1 file changed: 3 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/21432.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21432/head:pull/21432

PR: https://git.openjdk.org/jdk/pull/21432