RFR: 8275381 G1: refactor 2 constructors of G1CardSetConfiguration [v3]

[Hamlin Li]

> 2 constructors of G1CardSetConfiguration share some code, it's better to refacoring them to simplify the code.

Hamlin Li has updated the pull request incrementally with one additional commit since the last revision:

  Refine code further

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6033/files
  - new: https://git.openjdk.java.net/jdk/pull/6033/files/4908ac79..1cfcef49

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6033&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6033&range=01-02

  Stats: 87 lines in 3 files changed: 33 ins; 29 del; 25 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6033.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6033/head:pull/6033

PR: https://git.openjdk.java.net/jdk/pull/6033