Remove dependency from config files within `dss-test`

[amusingaxl]

This PR shed light on a problem that currently exists in spells-mainnet.

To be able to set up the root domain for L2s, spell tests are required to read the input config from dss-test. However, this seems like an abuse of such config file, as it is intended to be used only for the integration tests of dss-test itself.

Ideally, we want to move those configs to spells-mainnet itself for better maintainability.

[TheMarvelFan]

Hi @amusingaxl ,

I would like to learn more and work on this issue, if no one already is.

Thanks!