RFR: JDK-8318636: Add jcmd to print annotated process memory map

[Thomas Stuefe]

Analysts and supporters often use /proc/xx/maps to make sense of the memory footprint of a process.

Interpreting the memory map correctly can help when used as a complement to other tools (e.g. NMT). There even exist tools out there that attempt to annotate the process memory map with JVM information.

That, however, can be more accurately done from within the JVM, at least for mappings originating from hotspot. After all, we can correlate the mapping information in NMT with the VMA map.

Example output:

[example.system.map.txt](https://github.com/openjdk/jdk/files/13062903/example.system.map.txt)

This patch adds the VM annotations for VMAs that are *mmaped*. I also have an experimental patch that works with malloc'ed memory, but it is not ready yet for consumption and I leave that part of for now.

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Commit messages:
 - start

Changes: https://git.openjdk.org/jdk/pull/16301/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16301&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8318636
  Stats: 598 lines in 10 files changed: 597 ins; 1 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/16301.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16301/head:pull/16301

PR: https://git.openjdk.org/jdk/pull/16301