implement APG guidance (#8081)

* first pass at impementing AGP

* rename, cleanup code

* fix ruff

* fix modified cond to match ref impl better, support different cond arity

nodes.py

@@ -2261,6 +2261,7 @@ def init_builtin_extra_nodes():
         "nodes_optimalsteps.py",
         "nodes_hidream.py",
         "nodes_fresca.py",
+        "nodes_apg.py",
         "nodes_preview_any.py",
         "nodes_ace.py",
         "nodes_string.py",