Shift dependency on GenericJSON

[keeshux]

Most packages don't need to decode map internals, i.e. provider presets and VPN configurations, only the VPNImpl package does. Therefore, plug the dependency there and rely on generic [String: Any] in all the underlying packages.

• [ ] Host profile (de)deserialization
• [ ] Provider profile (de)serialization

[keeshux]

Actually, GenericJSON resolves a Codable limitation at the domain level. Codable needs a type to be defined in advance, which is why [String: Any] is not Codable. JSONSerialization does handle it though.

TL;DR: keep the dependency in Core.