pre-compute visitor method names on node classes

Store the visitor method name (e.g. "visit_If") as _visit_name on
each node class at definition time.  This avoids an f-string format
on every one of the ~500K visitor dispatch calls per compile.

src/jinja2/nodes.py

@@ -65,6 +65,7 @@ class NodeType(type):
             assert len(storage) == len(set(storage)), "layout conflict"
             d[attr] = tuple(storage)
         d.setdefault("abstract", False)
+        d["_visit_name"] = f"visit_{name}"
         return type.__new__(mcs, name, bases, d)
 
     def _classify_fields(cls, ns: dict[str, t.Any]) -> None:
@@ -191,7 +192,9 @@ class Node(metaclass=NodeType):
     attributes: tuple[str, ...] = ("lineno", "environment")
     abstract = True
 
-    #: Pre-classified field tuples, set by _init_field_classifications().
+    #: Pre-computed visitor method name and field tuples, set at class
+    #: definition time by the metaclass and _init_field_classifications().
+    _visit_name: t.ClassVar[str]
     _node_fields: t.ClassVar[tuple[str, ...]]
     _node_list_fields: t.ClassVar[tuple[str, ...]]
 

src/jinja2/visitor.py

@@ -30,7 +30,7 @@ class NodeVisitor:
         exists for this node.  In that case the generic visit function is
         used instead.
         """
-        return getattr(self, f"visit_{type(node).__name__}", None)
+        return getattr(self, type(node)._visit_name, None)
 
     def visit(self, node: Node, *args: t.Any, **kwargs: t.Any) -> t.Any:
         """Visit a node."""