RFR: 8276670: G1: Rename G1CardSetFreePool and related classes [v2]

[Albert Mingkun Yang]

On Thu, 25 Nov 2021 04:12:46 GMT, Hamlin Li <mli at openjdk.org> wrote:

>> As G1CardSetFreePool and related classes are going to be reused outside of the remembered set, they should be renamed.
>
> Hamlin Li has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Albert review

1. There are still a few places where `G1SegmentedArrayFreePool<mtGCCardSet>` is used, instead of `G1CardSetFreePool`. I am not entirely sure if that's intended.

2. It's undesirable to include some `buffer -> segment` renames in this PR.

Both are very subjective though.

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Marked as reviewed by ayang (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/6514