docs: document any_changed, all_changed

docs/using-operations.rst

@@ -166,6 +166,11 @@ All operations return an operation meta object which provides information about
         _if=lambda: create_user.did_change() or create_otheruser.did_change(),
     )
 
+    # The functions `any_changed` and `all_changed` are provided for common use cases, e.g.
+    from pyinfra.operations.utils import any_changed, all_changed
+    server.shell(commands=["..."], _if=any_changed(create_user, create_otheruser))
+    server.shell(commands=["..."], _if=all_changed(create_user, create_otheruser))
+
 Operation Output
 ~~~~~~~~~~~~~~~~