RFR: 8331858: [nmt] VM.native_memory statistics should work in summary mode

[Sonia Zaldana Calles]

Hi all, 

This PR addresses [8331858](https://bugs.openjdk.org/browse/JDK-8331858) enabling the "statistics" sub-option for jcmd VM.native_memory. 

Since [8256844](https://bugs.openjdk.org/browse/JDK-8256844), preinit state gets printed under "statistics" and this is also relevant for the summary state. 

Testing:
- [x] Added test case passes. 

Thanks!

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Commit messages:
 - 8331858: [nmt] VM.native_memory statistics should work in summary mode

Changes: https://git.openjdk.org/jdk/pull/19179/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19179&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8331858
  Stats: 75 lines in 3 files changed: 65 ins; 0 del; 10 mod
  Patch: https://git.openjdk.org/jdk/pull/19179.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19179/head:pull/19179

PR: https://git.openjdk.org/jdk/pull/19179