RFR: DRAFT: Expand old on demand

[Kelvin Nilsen]

This PR describes several proposed changes to dynamically adjust the sizes of old-gen and young-gen.  In general, the objective is to keep old-gen as small as possible so that there is an abundance of memory available for the young-gen allocation runway.

As currently drafted, there are regression failures.  This DRAFT PR is published for the purpose of facilitating a careful code review.

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Commit messages:
 - Fix more whitespace errors
 - Fix whitespace errors
 - Remove extraneous whitespace and instrumentation
 - Fix a missing curly brace (manual merge conflict resolution error)
 - Merge remote-tracking branch 'GitFarmBranch/expand-old-on-demand' into expand-old-on-demand
 - Fix indentation and brace nesting in ShenandoahFreeSet::allocate_single
 - Add asserts to assure fill_objects are sufficiently large
 - Fix initialization error and add object registration for fill  object
 - Disable over-zealous assertions
 - Disable redundant calculation of generation usage
 - ... and 65 more: https://git.openjdk.org/shenandoah/compare/d6df935b...40ba78b4

Changes: https://git.openjdk.org/shenandoah/pull/248/files
 Webrev: https://webrevs.openjdk.org/?repo=shenandoah&pr=248&range=00
  Stats: 3097 lines in 35 files changed: 1812 ins; 757 del; 528 mod
  Patch: https://git.openjdk.org/shenandoah/pull/248.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah.git pull/248/head:pull/248

PR: https://git.openjdk.org/shenandoah/pull/248