Draft: v0.5.0: Linuxfd usage + Ruff for python 3.13 + split EcsCoreAgent::initialize_subagents into 3 sub-methods

Contains the commits from !28 (merged), !29 (merged) and !30 (merged)

• Changes needed to operate with Python 3.13 under Ubuntu 24.04 (mfles cluster)
• One change allowing more granular initialization of subagents in EcsCoreAgent, linked to tests with TFC2 (higher layers changes abandoned after reaching dead-end, but still needed in a few weeks)
• Using linuxfd timer and event file-descriptors to replace periodic timouts with proper polling in loop threads of EcsCmdCore
  • Right now only the emission loop and pingers (emission side timed/repeated Actions)

TODO:

• DCA Alarm Pub-Sub generic interface, Sub side in CommandCore cf https://git.cbm.gsi.de/walters-test-environment/dca-prototype/-/issues/118
• DCA Alarm mapping to "handler method", per categories - [ ] Alarms cf https://git.cbm.gsi.de/walters-test-environment/dca-prototype/-/issues/135 and https://git.cbm.gsi.de/walters-test-environment/dca-prototype/-/issues/144 - [ ] Alerts = monitoring
• DCA Alarm wake-up/reception in Execution loop (per category?)