RFR: 8318026: jcmd should provide access to detailed JVM object information [v15]

[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 incrementally with two additional commits since the last revision:

 - Update decode_raw usage to decode_without_asserts, after 8328698
 - nits

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/17655/files
  - new: https://git.openjdk.org/jdk/pull/17655/files/510feaa1..7e6c7b97

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17655&range=14
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17655&range=13-14

  Stats: 7 lines in 2 files changed: 0 ins; 4 del; 3 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