[jdk17u-dev] RFR: 8287596: Reorg jdk.test.lib.util.ForceGC

[Goetz Lindenmaier]

I backport this test infra improvement to keep 17 close to 21. 
It also simplifies backport of  JDK-8300727.

Clean except of a row of files left out because they are not in 17.
I could not find another call to await of ForceGC in the tests.
Will mark as clean.

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Depends on: https://git.openjdk.org/jdk17u-dev/pull/1860

Commit messages:
 - Backport 82a8bd7e92a1867b0c82f051361938be8610428d

Changes: https://git.openjdk.org/jdk17u-dev/pull/1861/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=1861&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8287596
  Stats: 83 lines in 6 files changed: 13 ins; 34 del; 36 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/1861.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/1861/head:pull/1861

PR: https://git.openjdk.org/jdk17u-dev/pull/1861