RFR: 8332448: Make SpaceMangler inherit AllStatic

[Albert Mingkun Yang]

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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Commit messages:
 - mangle

Changes: https://git.openjdk.org/jdk/pull/19279/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19279&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8332448
  Stats: 518 lines in 26 files changed: 9 ins; 486 del; 23 mod
  Patch: https://git.openjdk.org/jdk/pull/19279.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19279/head:pull/19279

PR: https://git.openjdk.org/jdk/pull/19279