RFR: 8319948: jcmd man page needs to be updated

[David Holmes]

Please review these missing updates to the `jcmd` manpage - see JBS issue for details.

I also fixed the sub-command ordering in a few places and a couple of minor formatting fixes.

Thanks to @tstuefe for collating the initial information on what was missing. I used to `jcmd help <cmd>` option to compare the help text with the manpage text and adjusted the manpage accordingly (and found a few more omissions - some of which will be fixed by follow up RFE by the respective owners).

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Commit messages:
 - 8319948: jcmd man page needs to be updated

Changes: https://git.openjdk.org/jdk/pull/17213/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17213&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8319948
  Stats: 262 lines in 1 file changed: 175 ins; 56 del; 31 mod
  Patch: https://git.openjdk.org/jdk/pull/17213.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17213/head:pull/17213

PR: https://git.openjdk.org/jdk/pull/17213