Swagger refactor/cleanup

* Remove duplicate or unused types and constants
* Move all documetation-only models and responses into swagger package
* Remove all unecessary names, go-swagger will determine names from
  struct declarations
* Use Libpod suffix to differentiate between compat and libpod models
  and responses. Taken from swagger:operation declarations.
* Models and responses that start with lowercase are for swagger use
  only while uppercase are used "as is" in the code and swagger comments
* Used gofumpt on new code

```release-note

```

Signed-off-by: Jhon Honce <jhonce@redhat.com>

pkg/api/server/register_generate.go

@@ -103,7 +103,7 @@ func (s *APIServer) registerGenerateHandlers(r *mux.Router) error {
 	//       additionalProperties:
 	//         type: string
 	//   500:
-	//     $ref: "#/responses/InternalError"
+	//     $ref: "#/responses/internalError"
 	r.HandleFunc(VersionedPath("/libpod/generate/{name:.*}/systemd"), s.APIHandler(libpod.GenerateSystemd)).Methods(http.MethodGet)
 
 	// swagger:operation GET /libpod/generate/kube libpod GenerateKubeLibpod
@@ -127,15 +127,16 @@ func (s *APIServer) registerGenerateHandlers(r *mux.Router) error {
 	//    default: false
 	//    description: Generate YAML for a Kubernetes service object.
 	// produces:
+	// - text/vnd.yaml
 	// - application/json
 	// responses:
 	//   200:
-	//     description: no error
+	//     description: Kubernetes YAML file describing pod
 	//     schema:
 	//      type: string
 	//      format: binary
 	//   500:
-	//     $ref: "#/responses/InternalError"
+	//     $ref: "#/responses/internalError"
 	r.HandleFunc(VersionedPath("/libpod/generate/kube"), s.APIHandler(libpod.GenerateKube)).Methods(http.MethodGet)
 	return nil
 }