RFR: 8277946: NMT: Deprecate and remove VM.native_memory shutdown jcmd command option

[Zhengyu Gu]

NMT shutdown functionality is a remnant of its first implementation, which could consume excessive amount of memory, therefore, it needed capability to shut it self down to ensure health of JVM. This is no longer a case for new implementation.

NMT shutdown can be requested via Jcmd. However, it is rare used.

We should deprecate for shutdown Jcmd command for removing NMT shutdown functionality.

Corresponding [CSR](https://bugs.openjdk.java.net/browse/JDK-8277947) has been approved.

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Commit messages:
 - v0

Changes: https://git.openjdk.java.net/jdk/pull/6618/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6618&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8277946
  Stats: 133 lines in 5 files changed: 0 ins; 131 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6618.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6618/head:pull/6618

PR: https://git.openjdk.java.net/jdk/pull/6618