Decouple protodepUp task from zio-grpc

[thesamet]

Thanks for putting this plugin together! I think the plugin can become more modular if users of ProtodepPlugin can use it without opting in to zio-grpc. To accomplish this, protoDepUpTask can be moved to ProtodepPlugin, and GrpcDependencies can enable ProtoDep (rather than the other way around). This would let users who use ProtodepPlugin but not GrpcDependencies to set their own PB.targets.

[vigoo]

Thanks! I agree, this came out from an internal project where we are using it for zio-grpc projects, but could be more generic.