RFR: 8292407: Improve Weak CAS VarHandle/Unsafe tests resilience under spurious failures [v2]

[Aleksey Shipilev]

> We have a few reports that existing Weak* VarHandle tests are still flaky, for example on large AArch64 machines or small RISC-V machines.
> 
> The flakiness is intrinsic to the nature of Weak* operations under tests, that can spuriously fail. The last attempt to fix these was [JDK-8155739](https://bugs.openjdk.org/browse/JDK-8155739). We need to strengthen these a bit more.
> 
> The actual values depend on the successful testing on known-failing platforms. I ballparked bumping the attempts 5x and introducing the delay would help without exploding test time in worst cases.

Aleksey Shipilev has updated the pull request incrementally with two additional commits since the last revision:

 - Update copyrights
 - Also do Unsafe tests

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/9889/files
  - new: https://git.openjdk.org/jdk/pull/9889/files/56e8f65a..b4f3890c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9889&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9889&range=00-01

  Stats: 410 lines in 47 files changed: 344 ins; 0 del; 66 mod
  Patch: https://git.openjdk.org/jdk/pull/9889.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9889/head:pull/9889

PR: https://git.openjdk.org/jdk/pull/9889