RFR: 8365880: Shenandoah: Unify memory usage accounting in ShenandoahFreeSet [v32]

[Kelvin Nilsen]

> This PR eliminates redundant bookkeeping that had been carried out by both ShenandoahGeneration and ShenandoahFreeSet.  In the new code, we keep a single tally of relevant information within ShenandoahFreeSet.
> Queries serviced by ShenandoahGeneration are now delegated to ShenandoahFreeSet.
> 
> This change eliminates rare and troublesome assertion failures that were often raised when the ShenandoahFreeSet tallies did not match the ShenandoahGeneration tallies.  These assertion failures resulted because the two sets of books are updated at different times, using different synchronization mechanisms.
> 
> The other benefit of this change is that we have less synchronization overhead because we only have to maintain a single set of books.

Kelvin Nilsen has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 154 commits:

 - Merge remote-tracking branch 'jdk/master' into freeset-has-authoritative-tallies
 - Rework implementation of CompressedClassSpaceSizeInJmapHeap.java
 - fix errors in CompressedClassSpaceSizeInJmapHeap.java
 - Add debug instrumentation to CompressedClassSpaceSizeInJmapHeap.java
 - Add sleep to CompressedClassSpaceSizeInJmapHeap.java test
 - Fix up vmstructs and other infrastructure for jmap heap dump
 - After initialization, check for SoftMaxHeapSize changed by constraints enforcement
 - clamp SoftMaxHeapSize during initialization
 - revert change to SoftMaxHeapSizeConstraintFunc
 - fix anothr override declaration
 - ... and 144 more: https://git.openjdk.org/jdk/compare/97e5ac6e...abf9b1f8

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Changes: https://git.openjdk.org/jdk/pull/26867/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26867&range=31
  Stats: 3529 lines in 44 files changed: 2120 ins; 1005 del; 404 mod
  Patch: https://git.openjdk.org/jdk/pull/26867.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26867/head:pull/26867

PR: https://git.openjdk.org/jdk/pull/26867