RFR: 8258142: Simplify G1RedirtyCardsQueue

[Kim Barrett]

Please review this change to G1RedirtyCardsQueue to separate the local qset
from the queue. This simplifies the implementation, though requires clients
to deal with the local qset explicitly. This is an enabling step toward
desired simplifications of the PtrQueue hierarchy. This change also
simplifies the interaction between the local qset and the global qset.

Testing:
mach5 tier1-5

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Commit messages:
 - separate local redirty qset from redirty queue

Changes: https://git.openjdk.java.net/jdk/pull/1755/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1755&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8258142
  Stats: 79 lines in 5 files changed: 16 ins; 32 del; 31 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1755.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1755/head:pull/1755

PR: https://git.openjdk.java.net/jdk/pull/1755