RFR: 8373225: GenShen: More adaptive old-generation growth heuristics [v3]

[Kelvin Nilsen]

> When old-gen consumes a small percentage of heap size, trigger when old-gen expands by more than ShenandoahMinOldGenGrowthPercent, with default value 50%, from the live data in old at time of previous old-gen mark.
> 
> When old-gen consumes a larger percentage of heap size, we trigger when old-gen expands by more than  ShenandoahMinOldGenGrowthRemainingHeapPercent, with default value 25%, of the memory not live in old at the last marking of old.

Kelvin Nilsen has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 12 additional commits since the last revision:

 - Merge remote-tracking branch 'jdk/master' into more-adaptive-old-triggers-gh
 - Add comment to describe behavior of adjust_old_garbage_threshold()
 - Simplify representation of growth percentages
 - Change default value of ShenandoahMinOldGenGrowthRemainingHeapPercent
 - make old evac ratio adaptive
 - Merge remote-tracking branch 'jdk/master' into more-adaptive-old-triggers
 - change default value of ShenandoahMinOldGenGrowthRemainingHeapPercent
 - Merge remote-tracking branch 'jdk/master' into more-adaptive-old-triggers
 - Adjust test for new defaults
 - Merge remote-tracking branch 'jdk/master' into more-adaptive-old-triggers
 - ... and 2 more: https://git.openjdk.org/jdk/compare/edebc413...c7c22974

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Changes:
  - all: https://git.openjdk.org/jdk/pull/28561/files
  - new: https://git.openjdk.org/jdk/pull/28561/files/d5e4072d..c7c22974

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28561&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28561&range=01-02

  Stats: 12179 lines in 61 files changed: 8415 ins; 3463 del; 301 mod
  Patch: https://git.openjdk.org/jdk/pull/28561.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28561/head:pull/28561

PR: https://git.openjdk.org/jdk/pull/28561