RFR: 8297033: G1: Improve logging for Remembered Sets [v2]

[Albert Mingkun Yang]

> Small change in logging for merging remset of eager reclaim candidates and collection set, in order to avoid confusion.
> 
> Test: hotspot_gc

Albert Mingkun Yang has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains two commits:

 - merge
 - g1-remset-log

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Changes: https://git.openjdk.org/jdk/pull/11165/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11165&range=01
  Stats: 75 lines in 3 files changed: 44 ins; 9 del; 22 mod
  Patch: https://git.openjdk.org/jdk/pull/11165.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11165/head:pull/11165

PR: https://git.openjdk.org/jdk/pull/11165