Refactor process spawning logic

[fzyzcjy]

Just to use CI to check WIP code sanity and code diff, do not review now :)

Motivation

Modifications

Checklist

• Format your code according to the Contributor Guide.
• Add unit tests as outlined in the Contributor Guide.
• Update documentation as needed, including docstrings or example tutorials.

[fzyzcjy]

Closed in favor of #2791