Debugger: Extend CLI stop command.

- "stop" now allows optionally specifying a thread ID to stop an arbitrary
thread in the team, rather than always targetting the current one.
Debugger: Implement #10283.

- When constructing the CLI interface, also pass along the target thread ID
if one was specified.
- If our only reason for starting is to save a report, and we've been given
a specific thread to target, rather than just a team, ensure that the target
thread is in a stopped state prior to saving the report.