[FEATURE] Route all configuration management through a single component

[shonfeder]

This ticket records a plan hatched in conversation with @Kukovec today.

The plans for the OutputManager introduced in #1025, and implemented in followups, calls for a "cascade loading" configuration system. The configuration is derived from reading

1. CLI arguments
2. environment variables
3. A local configuration file (perhaps with the location overridden by a CLI flag)
4. A global configuration file

The final configuration is computed based on the priority of the source.

Currently, we are doing this in a somewhat ad hoc way. But gathering all of this logic into a configuration management sub-system will help reduce the complexity of the OutputManager and contribute to the current plan to move it away from a singleton, into something we can put in DI, that gets all of its configurations from the PassOptions.

With the server mode coming down the pipe, we'll have more need for a configuration system that is easy to maintain.

Scope of work expected to resolve this ticket:

• Briefly research existing configuration management systems used in the Scala ecosystem.
• Decide whether to use one of the existing solutions or roll our own.
• Write a short ADR recording the decisions.
• Move the configuration parsing out of the OutputManager and into the new subsystem.