RFR: 8281114: G1: Remove PreservedMarks::init_forwarded_mark

[Albert Mingkun Yang]

On Wed, 2 Feb 2022 11:24:24 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Simple change of inlining `PreservedMarks::init_forwarded_mark` and removing it. This decouples G1 self-forwarded obj handling from preserved marks.
> 
> Test: build

Thanks for the review.

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PR: https://git.openjdk.java.net/jdk/pull/7321