RFR: 8331858: [nmt] VM.native_memory statistics should work in summary mode [v2]

[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!

Sonia Zaldana Calles has updated the pull request incrementally with one additional commit since the last revision:

  Addressing feedback

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/19179/files
  - new: https://git.openjdk.org/jdk/pull/19179/files/a088a8f1..8df83d14

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=19179&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19179&range=00-01

  Stats: 4 lines in 2 files changed: 0 ins; 1 del; 3 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