The main goal here is to move towards more self contained node
definitions. Previously, one would have to change `blenkernel` to
add a new node which is not necessary anymore. There is no need
for all these register functions to "leak out" of the nodes module.
Differential Revision: https://developer.blender.org/D16612
* This patch just moves runtime data to the runtime struct to cleanup
the dna struct. Arguably, some of this data should not even be there
because it's very use case specific. This can be cleaned up separately.
* `miniwidth` was removed completely, because it was not used anywhere.
The corresponding rna property `width_hidden` is kept to avoid
script breakage, but does not do anything (e.g. node wrangler sets it).
* Since rna is in C, some helper functions where added to access the
C++ runtime data from rna.
* This size of `bNode` decreases from 432 to 368 bytes.
