RFR: 8360790: G1: Improve HRRSStatsIter name

[Thomas Schatzl]

Hi all,

  please review this change that changes the names of some internal classes related to remembered set summaries to use the G1 prefix.

Testing: gha

Thanks,
  Thomas

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Commit messages:
 - 8360790

Changes: https://git.openjdk.org/jdk/pull/26042/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26042&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8360790
  Stats: 18 lines in 1 file changed: 0 ins; 1 del; 17 mod
  Patch: https://git.openjdk.org/jdk/pull/26042.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26042/head:pull/26042

PR: https://git.openjdk.org/jdk/pull/26042