fix: address CI failures from env var migration

- Add apps:set subcommand for managing apps properties (mirrors
  ps:set, scheduler:set, builder:set pattern)
- Update nginx-vhosts functions/pre-disable-vhost/pre-enable-vhost
  to read proxy port from properties instead of config vars
- Fix test commands to use correct property-setting approaches:
  prop binary for ports properties, apps:set for apps properties

plugins/apps/src/commands/commands.go

@@ -28,6 +28,7 @@ Additional commands:`
     apps:locked <app>, Checks if an app is locked for deployment
     apps:rename <old-app> <new-app>, Rename an app
     apps:report [<app>] [<flag>], Display report about an app
+    apps:set <app>|--global <key> <value>, Set or clear an apps property
     apps:unlock <app>, Unlocks an app for deployment`
 )