RFR: 8288532: additional review changes for JDK-8286830

[Daniel D. Daugherty]

Update a couple of tests that were modified by JDK-8286830. Now the tests properly
honor any specified time limit by splitting the time between both sub-tests.
Also pick up a sanity check based on JDK-8288497 that I've been using in recent
stress testing.

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Depends on: https://git.openjdk.org/jdk19/pull/21

Commit messages:
 - update after 8288497 v01 code review changes
 - Merge branch 'JDK-8288139' into JDK-8288532
 - update after 8288497 v00 code review changes
 - Merge branch 'JDK-8288139' into JDK-8288532
 - 8288532: additional review changes for JDK-8286830

Changes: https://git.openjdk.org/jdk19/pull/32/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk19&pr=32&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8288532
  Stats: 12 lines in 3 files changed: 9 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk19/pull/32.diff
  Fetch: git fetch https://git.openjdk.org/jdk19 pull/32/head:pull/32

PR: https://git.openjdk.org/jdk19/pull/32