feat: add standby URL, change default standby port (#287)

This PR introduces a new environment variable with standby URL, it also
changes the default port for the standby port env var.

---------

Co-authored-by: František Nesveda <[email protected]>

Author: jirimoravcik

src/apify/_configuration.py

@@ -259,7 +259,15 @@ class Configuration(CrawleeConfiguration):
             description='TCP port for the Actor to start an HTTP server to receive messages in the Actor Standby mode',
         ),
         deprecated('Use `web_server_port` instead'),
-    ] = 4322
+    ] = 4321
+
+    standby_url: Annotated[
+        str,
+        Field(
+            alias='actor_standby_url',
+            description='URL for accessing web servers of Actor runs in Standby mode',
+        ),
+    ]
 
     token: Annotated[
         str | None,
@@ -296,7 +304,7 @@ class Configuration(CrawleeConfiguration):
                 'actor_web_server_url',
                 'apify_container_url',
             ),
-            description='Unique public URL for accessing the Actor run web server from the outside world',
+            description='Unique public URL for accessing a specific Actor run web server from the outside world',
         ),
     ] = 'http://localhost:4321'