[jdk17u-dev] RFR: 8277990: NMT: Remove NMT shutdown capability

[Thomas Stuefe]

This removes the NMT shutdown machinery from hotspot. For details, please see the associated JBS issue, as well as the companion change https://bugs.openjdk.org/browse/JDK-8277946 and CSR https://bugs.openjdk.org/browse/JDK-8277947.

This is not a clean backport, but the fixes are very minor:

- the original patch changes perfmemory_posix.cpp, but this hunk is not needed in JDK17
- A small fix was needed since the "shutdown" dcmd option in JDK17 had been deprecated out of carefulness, not outright removed: https://github.com/openjdk/jdk17u-dev/commit/5ce36d6c210d265a59548bde2f9e53b73bfa5c6f . 

Testing:
I manually ran runtime/NMT and all gtest variants for NMT on linux x64 and x86.
SAP nightlies are scheduled.

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Commit messages:
 - Fix remaining mention of shutdown in dcmd
 - 8277990: NMT: Remove NMT shutdown capability

Changes: https://git.openjdk.org/jdk17u-dev/pull/1116/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=1116&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8277990
  Stats: 470 lines in 20 files changed: 35 ins; 353 del; 82 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/1116.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev pull/1116/head:pull/1116

PR: https://git.openjdk.org/jdk17u-dev/pull/1116