Description

The challenger instances are decoupled from L2 networks and their configuration is moving to the top-level configuration.

Notes

There are several larger motions in this PR aimed at laying down the groundwork for further improvements:

• The intermediate step of parsing the input to dict, then reformatting it to a struct has been removed. As it is, it adds no value and only creates room for error
• The input parser for challenger has been moved to its own file
• Challenger configuration is structured as a dictionary in YAML - this enforces unique and YAML-valid (no whitespace, etc) names, which removes the need for extra validation logic. The dictionary is then parsed into a list for ease of enumeration, and the names are added to the config objects themselves
• There is no default configuration for challenger (in the sense that there is no challengers.default_params object. Instead, YAML anchors can be utilised to share pieces of configuration. This removes the need for extra parsing logic and keeps things as lean as possible
• The config objects are enriched with service_name property. This will become important when it comes to resolving circular dependencies later on, as URLs will be possible to construct without having an instance of Service
• The ubiquitous mkdir && combined with sh -c entrypoint has been replaced (only for op-challenger) with a persistent directory.

Questions

@sigma there will be more objects where something points to a list of networks. I named the field participants so that later on we might expand it to cover both networks and interop sets (with a heterogeneous list of some sort, TBD). That okay? I want to avoid confusion with participants in chains that signify nodes rather than networks.

Related to ethereum-optimism/optimism#15611