RFR: 8318026: jcmd should provide access to detailed JVM object information [v16]

[Kevin Walls]

> Introduce the jcmd "VM.inspect" to implement access to detailed JVM object information.
> 
> Not recommended for live production use.  Requires UnlockDiagnosticVMOptions and not included in jcmd help output, to remind us this is not a general-purpose customer-facing tool.

Kevin Walls has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 33 additional commits since the last revision:

 - Merge remote-tracking branch 'upstream/master' into 8318026_jcmd_VMdebug_command
 - Update XX option
 - Update decode_raw usage to decode_without_asserts, after 8328698
 - nits
 - Merge remote-tracking branch 'upstream/master' into 8318026_jcmd_VMdebug_command
 - Update XX flag requirement
 - VMInspectTest update
 - Merge remote-tracking branch 'upstream/master' into 8318026_jcmd_VMdebug_command
 - One dbg_is_good_oop method
 - Test more pointer types: compiled method and metadata.
 - ... and 23 more: https://git.openjdk.org/jdk/compare/e5180fba...bb92a849

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/17655/files
  - new: https://git.openjdk.org/jdk/pull/17655/files/7e6c7b97..bb92a849

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17655&range=15
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17655&range=14-15

  Stats: 16719 lines in 562 files changed: 8816 ins; 4016 del; 3887 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