RFR: 8370887: DelayScheduler.replace method may break the 4-ary heap in certain scenarios

[Alan Bateman]

DelayScheduler.replace missing check to sift up when replaced with smaller value. checkHeap checks invariants when replacing. Executing tests with make run-test or other targets runs tests with -esa so assume is enabled.

New regression test to ensure delayed tests executes in expected delay order.

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Commit messages:
 - Test improvements
 - Initial commit

Changes: https://git.openjdk.org/jdk/pull/28469/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28469&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8370887
  Stats: 199 lines in 2 files changed: 181 ins; 8 del; 10 mod
  Patch: https://git.openjdk.org/jdk/pull/28469.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28469/head:pull/28469

PR: https://git.openjdk.org/jdk/pull/28469