Remove the 'procs' from lwps and use the one from procs.

OK mrg@

fix some minor issues in these user functions, and add more to
investigate lwps/processes:

- fix header formatting
- separate proc and thread info
- add per-thread and per-proc functions, use them a

fix some minor issues in these user functions, and add more to
investigate lwps/processes:

- fix header formatting
- separate proc and thread info
- add per-thread and per-proc functions, use them as building
blocks for the existing functions;
- 'threadinfo' to display just one thread,
- 'procthreadsaddr' to display one process by struct proc *
- 'procthreadspid' to find process by pid
- add 'procs' as a ps(1) a-like

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fix format

Add a command to dump all thread stacks in the system and a command to dump
lockdebug state.

Use the right pointer to traverse the proc's lwp list.

From PR 41788.

- Replace 'xps' with 'procs' and 'lwps'.
- Needs a bit more work.