8332448: Make SpaceMangler inherit AllStatic

[albertnetymk]

Extract the state for top out of SpaceMangler. Users (Serial and Parallel GC) already tracks the top before/after GC. The "real" change in this PR are only two places: serialFullGC.cpp and PSParallelCompact::post_compact.

Test: tier1-5

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Progress

• [ ] Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• [x] Change must not contain extraneous whitespace
• [x] Commit message must refer to an issue

Issue

• JDK-8332448: Make SpaceMangler inherit AllStatic (Enhancement - P4)

Reviewing

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Update a local copy of the PR:
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$ git pull https://git.openjdk.org/jdk.git pull/19279/head

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