RFR: 8315044: GenShen: Verifier detects clean card should be dirty [v2]

[Kelvin Nilsen]

> When a Reference object is newly discovered, it is placed onto the worker's thread-local discovered list.  This sometimes results in a reference from an old object to a young object, requiring that the remembered set card-table entry be marked as dirty.  This patch causes the marking to be performed.

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

  Also update card table when moving discovered References to global list

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Changes:
  - all: https://git.openjdk.org/shenandoah/pull/314/files
  - new: https://git.openjdk.org/shenandoah/pull/314/files/dc95476c..8b898a56

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=shenandoah&pr=314&range=01
 - incr: https://webrevs.openjdk.org/?repo=shenandoah&pr=314&range=00-01

  Stats: 22 lines in 1 file changed: 20 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/shenandoah/pull/314.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah.git pull/314/head:pull/314

PR: https://git.openjdk.org/shenandoah/pull/314