RFR: 8350889: GenShen: Break out of infinite loop of old GC cycles

[Kelvin Nilsen]

Add log message when heuristic trigger because previous trigger is pending.  Cancel the pending-trigger condition for old-generation at the start of old-generation GC.

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Commit messages:
 - Fix white space
 - Cancel pending GC trigger at start of old gc
 - Merge branch 'openjdk:master' into master
 - Merge branch 'openjdk:master' into master
 - Merge branch 'openjdk:master' into master
 - Merge branch 'openjdk:master' into master
 - Merge branch 'openjdk:master' into master
 - Merge branch 'openjdk:master' into master
 - Merge branch 'openjdk:master' into master
 - Merge branch 'openjdk:master' into master
 - ... and 20 more: https://git.openjdk.org/jdk/compare/3c9d64eb...85319914

Changes: https://git.openjdk.org/jdk/pull/23827/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23827&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8350889
  Stats: 2 lines in 2 files changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/23827.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23827/head:pull/23827

PR: https://git.openjdk.org/jdk/pull/23827