[jdk11u-dev] RFR: 8292407: Improve Weak CAS VarHandle/Unsafe tests resilience under spurious failures

[Fei Yang]

Backport this test-only change in order to help "weak" and slow platforms to have stable results. Doing in advance of RISC-V port in https://github.com/openjdk/riscv-port-jdk11u where this helps to get stable test results.

Original patch does not apply cleanly as the dependent bug https://bugs.openjdk.org/browse/JDK-8218471 was only partially backported. So there are some conflicts in file test/hotspot/jtreg/compiler/unsafe/X-UnsafeAccessTest.java.template and the auto-generated tests from this template file.

Testing
- [ ] GHA (updated tests are part of tier1)

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Commit messages:
 - Merge remote-tracking branch 'upstream/master' into backport-8292407
 - JDK-8292407

Changes: https://git.openjdk.org/jdk11u-dev/pull/2099/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2099&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8292407
  Stats: 951 lines in 45 files changed: 800 ins; 0 del; 151 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2099.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2099/head:pull/2099

PR: https://git.openjdk.org/jdk11u-dev/pull/2099