Switch to env-var-based development config definitions

[acelaya]

Once #2220 is merged, we will have moved the default values for env vars to EnvVars enum.

This means we could remove most of the local dev config files (at least those that map to options objects), and instead use env vars for custom values in development as well, by using a .env file that's loaded via docker compose, for example.

This will also allow to read env vars anywhere, rather than having to remember the value should be set in config files only, and also ensure the env-var:read command returns consistent values in dev environments as well.

Additionally, we could remove the dependency that is used to map options objects from config, and instead read env vars directly to set their default values.