[jdk11u-dev] RFR: 8239265: JFR: Test cleanup of jdk.jfr.api.consumer package

[Joshua Cao]

clean backport. Primary motivation for this backport is that this patch is a dependency of [8242188](https://bugs.openjdk.org/browse/JDK-8242188), which fixes a JFR test bug. Opening a separate PR for that.

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Commit messages:
 - 8239265: JFR: Test cleanup of jdk.jfr.api.consumer package

Changes: https://git.openjdk.org/jdk11u-dev/pull/1326/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=1326&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8239265
  Stats: 557 lines in 18 files changed: 127 ins; 157 del; 273 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/1326.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev pull/1326/head:pull/1326

PR: https://git.openjdk.org/jdk11u-dev/pull/1326