RFR: 8319342: GenShen: Reset the count of degenerated cycles in a row following Full GC [v2]

[Kelvin Nilsen]

> After a Full GC completes, reset the count on consecutive degenerated cycles to zero.  This prevents automatic triggering of back-to-back Full GC.

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

  Respond to reviewer feedback
  
  Restore the original ShenandoahHeuristics::should_degenerate_cycle() so
  that ShenandoahPassiveHeuristics can differentate from other
  implementations.
  
  Improve instance variable names.

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Changes:
  - all: https://git.openjdk.org/shenandoah/pull/352/files
  - new: https://git.openjdk.org/shenandoah/pull/352/files/3b3a1672..8bd0b992

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=shenandoah&pr=352&range=01
 - incr: https://webrevs.openjdk.org/?repo=shenandoah&pr=352&range=00-01

  Stats: 39 lines in 7 files changed: 19 ins; 10 del; 10 mod
  Patch: https://git.openjdk.org/shenandoah/pull/352.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah.git pull/352/head:pull/352

PR: https://git.openjdk.org/shenandoah/pull/352