[jdk17u-dev] RFR: 8300693: Lower the compile threshold and reduce the iterations of warmup loop in VarHandles tests

[Aleksey Shipilev]

Clean backport to improve test times.

Additional testing: 
 - [x] macos-aarch64-server-fastdebug, `java/lang/VarHandles`

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Commit messages:
 - Backport 86fed79670c109fc3a7fbe1eb2b1485c6dd99e2f

Changes: https://git.openjdk.org/jdk17u-dev/pull/1538/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=1538&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8300693
  Stats: 202 lines in 27 files changed: 74 ins; 30 del; 98 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/1538.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/1538/head:pull/1538

PR: https://git.openjdk.org/jdk17u-dev/pull/1538