RFR: 8275735: [linux] Remove deprecated Metrics api (kernel memory limit)

[Severin Gehwolf]

Please review this change to remove some API which no longer works as expected as recent OCI runtimes start to drop support for `--kernel-memory` switch. See the bug for references. This part of the API is not present in hotspot code.

Testing: Container tests (cgroup v1) on Linux x86_64 (all pass)

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Commit messages:
 - 8275735: [linux] Remove deprecated Metrics api (kernel memory limit)

Changes: https://git.openjdk.java.net/jdk/pull/6156/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6156&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8275735
  Stats: 104 lines in 6 files changed: 0 ins; 100 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6156.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6156/head:pull/6156

PR: https://git.openjdk.java.net/jdk/pull/6156