miscellaneous refactoring

Summary

• chore: fix the annoying static mut compilation warnings

• refactor: introduce ability to initialize a dummy Node for testing

• refactor: use non-joinable fibers for internal loops

• chore: tweaks to node::global()

• Change error type
• Use add_of!() macro

• chore: don't use sbroad logging macros in picodata code

It results in compilation warnings because of missing feature mock

• refactor: simplify generic iterator code in plugins a bit

I still don't like this version, because we now have at least 3 instantiations of stop_background_jobs, which is pretty massive. The better solution would be to collect the iterators into a Vec and pass the slice to the function, which would make it so the final binary only has 1 version of it. But the source code is a little bit more readable in the current version, and considering how nobody cares that picodata's release binary weighs 166MB...

• refactor: rework ServiceState, move ServiceId outside the mutex

This change makes it so we don't have to lock the fiber mutex in some cases.

• refactor: use TopologyCache in a couple of places in info.rs

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• Cherry-pick to: none
• Docs follow-up: not necessary
• Changelog is updated