feat: allow specifying a single process type to restart

This changes restarts to drop the 'release' part that currently gets triggered, which also helps reduce the possibility that a new image layer will be added due to predeploy deploy triggers.

Note that the old method essentially halfway-rebuilt the app (which was what added the extra layer). This refactor removes that, which is a bc-break.

Additionally, scaling processes will result in deploying _only_ restarting the processes being scaled.

Closes #2184

plugins/apps/functions.go

@@ -52,7 +52,7 @@ func destroyApp(appName string) error {
 
 	common.LogInfo1(fmt.Sprintf("Destroying %s (including all add-ons)", appName))
 
-	imageTag, _ := common.GetRunningImageTag(appName)
+	imageTag, _ := common.GetRunningImageTag(appName, "")
 	if err := common.PlugnTrigger("pre-delete", []string{appName, imageTag}...); err != nil {
 		return err
 	}