Add support for dev-only nodes. (#12106)

When a node is declared as dev-only, it doesn't show in the default UI
unless the dev mode is enabled in the settings. The intention is to
allow nodes related to unit testing to be included in ComfyUI
distributions without confusing the average user.

comfy/comfy_types/node_typing.py

@@ -236,6 +236,8 @@ class ComfyNodeABC(ABC):
     """Flags a node as experimental, informing users that it may change or not work as expected."""
     DEPRECATED: bool
     """Flags a node as deprecated, indicating to users that they should find alternatives to this node."""
+    DEV_ONLY: bool
+    """Flags a node as dev-only, hiding it from search/menus unless dev mode is enabled."""
     API_NODE: Optional[bool]
     """Flags a node as an API node. See: https://docs.comfy.org/tutorials/api-nodes/overview."""