RFR: 8308342: Remove MetaspaceClosure::Ref::keep_after_pushing()

[Calvin Cheung]

On Thu, 18 May 2023 05:12:35 GMT, Ioi Lam <iklam at openjdk.org> wrote:

> More CDS clean up:
> 
> - Remove the field `SourceObjInfo::_ref` since we have already cached its contents in fields such as `SourceObjInfo::_msotype` and `SourceObjInfo::_source_addr` 
> - Since there's no need to keep the `_ref` around, we can remove the `Ref::keep_after_pushing()` API.
> - Also `ArchiveBuilder::clean_up_src_obj_table()` is no longer necessary.

LGTM.

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Marked as reviewed by ccheung (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/14042#pullrequestreview-1435140870