RFR: 8290357: Drop HeapRegion::marked_bytes() [v3]

[Thomas Schatzl]

> Hi all,
> 
>   please review this removal of the `HeapRegion::_marked_bytes` member that records the bytes marked below tams in the recent mark as it is not really interesting in the removed places. I added comments to give reasons for this removal in the particular places for your review.
> 
> Testing: jtreg gc/g1, gha
> 
> Thanks,
>   Thomas

Thomas Schatzl has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains three commits:

 - Merge branch 'master' into 8290357-remove-marked-bytes
 - Remove actual member and references
 - initial version, use live_bytes instead of marked_bytes

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Changes: https://git.openjdk.org/jdk/pull/9511/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9511&range=02
  Stats: 52 lines in 8 files changed: 0 ins; 40 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/9511.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9511/head:pull/9511

PR: https://git.openjdk.org/jdk/pull/9511