Currently, the standard init function is called before socket
declaration, but the contextual init function is called after, which is
problematic if the declaration depends on the initialization step. This
patch moves the contextual init function to be called before declaration
just like the standard init function.
This is needed when moving the File Output node to use socket
declaration.
Pull Request: https://projects.blender.org/blender/blender/pulls/141203
fd24e1001a