RFR: JDK-8318636: Add jcmd to print annotated process memory map [v5]

[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 (from a spring petstore run):
> 
> [example_system_map.txt](https://github.com/openjdk/jdk/files/13179054/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.

Thomas Stuefe has updated the pull request incrementally with 11 additional commits since the last revision:

 - NMT_FLAGS_DO
 - small fixes
 - adapt test
 - remove test code
 - Use HANDLE_THREAD
 - move to nmt; split out MemFlagBitmap
 - Adjust output a la Gerard
 - dump to file, not to jcmd output stream
 - make it even fasterer
 - make it faster
 - ... and 1 more: https://git.openjdk.org/jdk/compare/a48b82c2...6033a64c

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/16301/files
  - new: https://git.openjdk.org/jdk/pull/16301/files/a48b82c2..6033a64c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16301&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16301&range=03-04

  Stats: 874 lines in 16 files changed: 445 ins; 400 del; 29 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