Blender Git Loki

Fix node_shader_utils problems with new mapping node

Since rBbaaa89a0bc54 we have to access the mapping node differently.
This doesnt take actual linkage of the new sockets into account (but
this wasnt done for most sockets on the Principled BSDF node either)

Also the min/max of the mapping node was removed entirely.
It was decided upon removing this from node_shader_utils as well (and
replace this by existing access to the Extension parameter of the
Texture node).

Part of solving T69526.

Differential Revision: https://developer.blender.org/D5693