RFR: 8303883: Confusing parameter name in G1UpdateRemSetTrackingBeforeRebuild::distribute_marked_bytes

[Thomas Schatzl]

Hi all,

  please review this change to de-confuse (imo) a parameter in `G1UpdateRemSetTrackingBeforeRebuild::distribute_marked_bytes`.

I also replaced some `SIZE_FORMAT` in the vicinity.

Testing: local jtreg gc test, GHA

Thanks,
  Thomas

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Commit messages:
 - initial version

Changes: https://git.openjdk.org/jdk/pull/12947/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12947&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8303883
  Stats: 29 lines in 2 files changed: 1 ins; 0 del; 28 mod
  Patch: https://git.openjdk.org/jdk/pull/12947.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12947/head:pull/12947

PR: https://git.openjdk.org/jdk/pull/12947