Add go package option in proto message files.

Context: The go_package option defines the import path of the package which will contain all the generated code for this file. The Go package name will be the last path component of the import path.

Issue: I got an error when moving the websocket packages to the pkg folder caused by generating a new set of proto files in the ignition_msgs package instead of just msgs (the package name we're using throughout the codebase)

Fix: Protobuf's been warning us that the go package declaration should be included, I think that's the reason why this is failing.

After applying these changes, everything works again.