RFR: 8272161: Make evacuation failure data structures local to collection

[Thomas Schatzl]

Hi all,

  can I have reviews for this change that moves some evacuation (failure) related data structures into the per-thread evacuation context (`G1ParThreadScanState`) which removes some young collection related code from G1CollectedHeap?

Testing: tier1-5

Thanks,
  Thomas

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Commit messages:
 - Minor cleanup
 - Make evacuation failure data structures local to collection

Changes: https://git.openjdk.java.net/jdk/pull/5066/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5066&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8272161
  Stats: 121 lines in 6 files changed: 42 ins; 45 del; 34 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5066.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5066/head:pull/5066

PR: https://git.openjdk.java.net/jdk/pull/5066