Upgrade to fabric-protos-go-apiv2

[mbrandenburger]

FSC is a heavy user of Fabric code, in particular, the fabric protos which are imported from github.com/hyperledger/fabric-protos-go. These protos require the us of github.com/golang/protobuf, which is deprecated and should be replaced by the google.golang.org/protobuf module.

github.com/hyperledger/fabric-protos-go-apiv2 provides updated fabric protos. However, as we still import code from the fabric repo we get an indirect dependency to the old fabric protos.