Manager update spring 2023

Inspired from looking into the manager code recently, it's time for some spring clean-up. There was quite a bit of cruft from calng's early days in the manager that at times is also responsible for strange UX moments. I tried to get rid on anything no longer needed and design it around the way we build pipeline nowadays:

• Remove support to spawn pipelines without group matchers
• Better distinction between domain devices (for purpose of scene generation) and managed devices (spawned by the manager)
• Support for more hardcoded managed keys, here for assemblers
• Instantiate entire pipeline concurrently
• Always auto-start ShmemTrainMatcher
• Gently force operators to restart the pipeline (at least devices) when device servers are changed
• Apply train stride setting after pipeline Instantiation

Didn't get around to testing yet, hence only draft.