Refactor to active_containers

[erwindouna]

Breaking change

Proposed change

Follow-up of: #167453 (comment)

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• This PR fixes or closes issue: fixes #
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Pull request overview

Refactors the Portainer coordinator’s container stats fetch logic to use clearer “active containers” terminology (running + paused), aligning naming with the actual behavior.

Changes:

• Renamed the intermediate list from running_containers to active_containers.
• Updated the accompanying comment to reflect that stats are fetched for running and paused containers.