ampinstmgr: Add each instance's sleep state to the output of appropriate operations

[ventaur]

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• I have searched for an existing feature request matching the description.

Feature Description

It would be very useful to some if ampinstmgr included each instance's sleep state in the output of the --ShowInstancesList and --ShowInstanceInfo operations, separately from its running state. This would allow callers to distinguish between stopped, running, and sleeping instances.

I intended to use ampinstmgr from a custom service that decides whether to suspend the server after all game instances are stopped or have been sleeping for 30+ minutes. For now, I'll go down the rabbit hole of using the API instead.

Thank you!