RFR: Expand old on demand [v47]

[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.
> 
> This PR now passes all GHA pre-integration tests and other internal CI tests.

Kelvin Nilsen has updated the pull request incrementally with one additional commit since the last revision:

  Modify API for ShenandoahHeapRegion::set_affiliation
  
  Remove the deferred_accounting argument and change the behavior so that
  this method never adjusts affiliated region counts.

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Changes:
  - all: https://git.openjdk.org/shenandoah/pull/248/files
  - new: https://git.openjdk.org/shenandoah/pull/248/files/d7b63412..f277f977

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=shenandoah&pr=248&range=46
 - incr: https://webrevs.openjdk.org/?repo=shenandoah&pr=248&range=45-46

  Stats: 68 lines in 5 files changed: 11 ins; 25 del; 32 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