RFR: 8315044: GenShen: Verifier detects clean card should be dirty [v3]

[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 with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:

 - Merge remote-tracking branch 'origin/master' into ref-processor-updates-remembered-set
 - Also update card table when moving discovered References to global list
 - Fix whitespace
 - Mark card as dirty if discovered reference list has interesting pointer

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Changes:
  - all: https://git.openjdk.org/shenandoah/pull/314/files
  - new: https://git.openjdk.org/shenandoah/pull/314/files/8b898a56..597a6e02

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=shenandoah&pr=314&range=02
 - incr: https://webrevs.openjdk.org/?repo=shenandoah&pr=314&range=01-02

  Stats: 189 lines in 18 files changed: 82 ins; 57 del; 50 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