RFR: 8334513: New test gc/TestAlwaysPreTouchBehavior.java is failing on MacOS aarch64

[Thomas Stuefe]

I exhumed this old issue that fell through the cracks.

The test wants to make sure AlwaysPreTouch works by pretouching the java heap and comparing RSS with heap size. 

This technique is shaky: if the host machine experiences memory pressure, part of the pretouched memory will be swapped out before we measure RSS.

There is no way to make this bulletproof; still, this test is too useful to abandon it. Therefore I modified this test to make false positives (hopefully) very unlikely. See comment in test for details.

See old PR: https://github.com/openjdk/jdk/pull/19803

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Commit messages:
 - wip
 - add missing Oracle copyright
 - start

Changes: https://git.openjdk.org/jdk/pull/25384/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25384&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8334513
  Stats: 90 lines in 5 files changed: 58 ins; 12 del; 20 mod
  Patch: https://git.openjdk.org/jdk/pull/25384.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25384/head:pull/25384

PR: https://git.openjdk.org/jdk/pull/25384