RFR: 8276670: G1: Move and rename G1CardSetFreePool and related classes [v5]

[Hamlin Li]

> Currently, only the card sets (remembered sets) use G1CardSetFreePool to give back memory to OS.
> 
> After JDK-8254739, this memory reclaiming mechanism could be reused by evacuation failure too. This is a preparation change to allow reuse of this code.
> 
> I plan to do this in about 3 steps to smooth the review process:
>   1. move G1CardSetFreePool and related classes to new file, rename these classes
>   2. refactor these classes to support freeing other freelist
>   3. some necessary cleanup
> 
> This is to simply move and rename G1CardSetFreePool and related classes, as G1CardSetFreePool and related classes are going to be reused outside of the remembered set, they should be factored out and renamed.
> Rename from G1CardSetXxx -> G1BufferListXxx.

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

  Rename card set to segmented array

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6289/files
  - new: https://git.openjdk.java.net/jdk/pull/6289/files/d7fb55c0..a51ebcd5

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6289&range=04
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6289&range=03-04

  Stats: 24 lines in 7 files changed: 1 ins; 1 del; 22 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6289.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6289/head:pull/6289

PR: https://git.openjdk.java.net/jdk/pull/6289