RFR: 8318026: jcmd should provide access to low-level JVM debug information

[Kevin Walls]

Introduce the jcmd "VM.debug" to implement access to a useful set of the established debug.cpp utilities, with "jcmd PID VM.debug subcommand ...".

Not recommended for live production use.  Calling these "debug" utilities, and not including them in the jcmd help output, is to remind us they are not general customer-facing tools.

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Commit messages:
 - Tidy up the safety checks
 - Whitebox not required, just check option properties.
 - unnecessary parameter to find
 - Test update. Recognise ZGC oops differently.  Formatting.
 - typo
 - Separate is_good_oop... method to avoid changing existing asserts.
 - More oop safety
 - 8318026: jcmd should provide access to low-level JVM debug information

Changes: https://git.openjdk.org/jdk/pull/17655/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17655&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8318026
  Stats: 371 lines in 5 files changed: 369 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/17655.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17655/head:pull/17655

PR: https://git.openjdk.org/jdk/pull/17655