RFR: Account for humongous object waste

[William Kemper]

The unused portion of the last region in a humongous object is now tracked and logged.

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Commit messages:
 - Revert unnecessary changes
 - Resolve merges
 - Merge branch 'shenandoah-master' into humongous-waste-accounting-fix
 - Merge branch 'shenandoah-master' into humongous-waste-accounting-fix
 - Remove instrumentation
 - WIP: Simplify computations of humongous waste
 - Simplify humongous waste tracking when region is recycled
 - WIP: Verify humongous waste tallies in verification
 - Merge branch 'shenandoah-master' into humongous-waste-accounting
 - Eliminate redundant compuation of generation usage after full gc
 - ... and 9 more: https://git.openjdk.org/shenandoah/compare/b2623500...e146bf7d

Changes: https://git.openjdk.org/shenandoah/pull/255/files
 Webrev: https://webrevs.openjdk.org/?repo=shenandoah&pr=255&range=00
  Stats: 108 lines in 8 files changed: 75 ins; 13 del; 20 mod
  Patch: https://git.openjdk.org/shenandoah/pull/255.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah.git pull/255/head:pull/255

PR: https://git.openjdk.org/shenandoah/pull/255