config: consolidate *config/Config and *dot/Config

[noot]

Task summary

• we currently have two configuration types defined in gossamer, first is *config/config.go which is used to unmarshal the toml config file, and the second is *dot/Config which is used to create the internal node services
• consolidate these two types into 1, this will require toml custom unmarshalling for some fields as the types don't match, eg LogLvl, Pruning, DiscoveryInterval