The compositor previously overloaded the vector type to represent
multiple dimensions that are always stored in a 4D float vector. This
patch introduce a dedicated type for float4, leaving the vector type to
always represent a 3D vector, which will be done in a later commit.
This is not exposed to the user as a separate socket type with a
different color, it is only an internal type that uses the same vector
socket shape and color.
Since the vector socket represents both 4D and 3D vectors, code
generally assumes that such sockets represents 3D vectors, and the
developer is expected to set it to a 4D vector if needed in the node
operation constructor, or use the newly added skip_type_conversion flag
for nodes that do not care about types, like the File Output node.
Though this should be redundant once we add a dimension property for
vector sockets.
Pull Request: https://projects.blender.org/blender/blender/pulls/134486
a5ecde48ae