RFR: 8295871: G1: Use different explicit claim marks for CLDs

[Thomas Schatzl]

Hi all,

  can I have reviews for this follow-up to [JDK-8295118](https://bugs.openjdk.org/browse/JDK-8295118) that removes the need to clear CLD claim marks for every full gc phase by using different claim values for the different phases.

Some comments:
* I used new g1 specific claim values instead of overloading the existing ones, which is imho clearer. I am open to better names, but something like `_claim_strong_2/3` seemed too cryptic. Then again, there is now a collector specific name in the enum. Maybe the enum values should be made collector-specific in some way? Currently they already are (e.g. `_claim_finalizable` is only used in ZGC) as G1 does not need the values except for (multiple) `_claim_strong`.
* I moved the CLD mark verification for the mark phase from `prepare_collection` to the constructor of `G1FullGCMarker`; I think this place is more fitting as directly above there is the use in the `CLDToOopClosure`. Also this pattern aligns with the use in the `G1FullGCAdjustTask`.

Testing: tier1-5

Thanks,
  Thomas

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Commit messages:
 - Missing include
 - Fix indentation
 - initial implementation

Changes: https://git.openjdk.org/jdk/pull/10989/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10989&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8295871
  Stats: 20 lines in 5 files changed: 7 ins; 5 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/10989.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10989/head:pull/10989

PR: https://git.openjdk.org/jdk/pull/10989