chore: Utility for resolving service dependencies

[janjakubnanista]

Description

PoC of a core utility that can resolve a launch sequence of a DAG of services (service in this case might be too strong of a word - since any items, non-service ones included, can be nodes in this DAG. I will use the word item instead since node is always a bit problematic in the world of blockchain nodes).

Prerequisites

• Items have predictable identifiers and provide external services a safe way of constructing these.. This means that, e.g., an EL client module needs to expose a function that can create an item name so that, e.g, a supervisor can specify that it depends on particular EL services to be live
• Items have launchers with identical signatures. This one is really just hinted here, and I want to let it simmer a bit - in this proposed solution, every item has a launch function that only accepts two arguments - plan and dependencies (a dictionary). In practice, this means that the input arguments would need to be carried inside this launch function.

Loose ends

• This solution embeds the launch function in the item. My instinct tells me this is not great.
• The test coverage on this needs to be expanded
• The error message for dependency cycles is kinda made up - it does not tell you where the dependency cycle is.