RFR: 8318594: NMT: VM.native_memory crashes on assert if functionality isn't supported by OS

[Afshin Zafari]

The case of unsupported call (`mincore`) is caught and returned `false`.
Tier1 tested.

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Commit messages:
 - 8318594: NMT: VM.native_memory crashes on assert if functionality isn't supported by OS

Changes: https://git.openjdk.org/jdk/pull/16540/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16540&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8318594
  Stats: 5 lines in 1 file changed: 5 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/16540.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16540/head:pull/16540

PR: https://git.openjdk.org/jdk/pull/16540