refactor: move all port management code to standalone ports plugin

This change makes interacting with port mappings more clear - folks might previously set the port mapping to the proxy type or vice-versa.

The existing proxy:ports* commands still exist but will show a deprecation warning for a single minor release.

plugins/proxy/proxy.go

@@ -1,8 +1,6 @@
 package proxy
 
 import (
-	"fmt"
-
 	"github.com/dokku/dokku/plugins/common"
 	"github.com/dokku/dokku/plugins/config"
 )
@@ -11,22 +9,6 @@ import (
 // and defaults to -1 (false)
 const RunInSerial = 0
 
-// PortMap is a struct that contains a scheme:host-port:container-port mapping
-type PortMap struct {
-	ContainerPort int
-	HostPort      int
-	Scheme        string
-}
-
-func (p PortMap) String() string {
-	return fmt.Sprintf("%s:%d:%d", p.Scheme, p.HostPort, p.ContainerPort)
-}
-
-// AllowsPersistence returns true if the port map is not to be persisted
-func (p PortMap) AllowsPersistence() bool {
-	return p.Scheme == "__internal__"
-}
-
 // BuildConfig rebuilds the proxy config for the specified app
 func BuildConfig(appName string) error {
 	return common.PlugnTrigger("proxy-build-config", []string{appName}...)