fix: implement missing cleanup routines

Without these, there was potential for configuration for certain plugins to continue to exist after an app was deleted.

plugins/nginx-vhosts/post-delete

@@ -1,12 +1,15 @@
 #!/usr/bin/env bash
 set -eo pipefail
 [[ $DOKKU_TRACE ]] && set -x
+source "$PLUGIN_CORE_AVAILABLE_PATH/common/property-functions"
 source "$PLUGIN_AVAILABLE_PATH/nginx-vhosts/functions"
 
 trigger-nginx-vhosts-post-delete() {
   declare desc="nginx-vhosts post-delete trigger"
   declare trigger="post-delete"
+  declare APP="$1"
 
+  fn-plugin-property-destroy "nginx" "$APP"
   restart_nginx "$@" >/dev/null
 }