Nodes: Add Factor and Percentage subtypes for vector sockets

This patch adds support for the Factor and Percentage subtypes for
vector sockets. This is needed by the compositor, since it has some node
inputs that specify locations and sizes relative to image size, and
having factor and percentage subtypes for those improves the UX quite a
bit according to user feedback.

Pull Request: https://projects.blender.org/blender/blender/pulls/138805

tests/python/bl_node_group_compat.py

@@ -48,6 +48,8 @@ subtype_idname = {
     ("BOOLEAN", "NONE"): "NodeSocketBool",
     ("ROTATION", "NONE"): "NodeSocketRotation",
     ("VECTOR", "NONE"): "NodeSocketVector",
+    ("VECTOR", "FACTOR"): "NodeSocketVectorFactor",
+    ("VECTOR", "PERCENTAGE"): "NodeSocketVectorPercentage",
     ("VECTOR", "TRANSLATION"): "NodeSocketVectorTranslation",
     ("VECTOR", "DIRECTION"): "NodeSocketVectorDirection",
     ("VECTOR", "VELOCITY"): "NodeSocketVectorVelocity",