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.
I 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). For the case of FBX this will loose the ability to clamp/
repeat independently in the two U/V axes, but it was agreed that this is
an acceptable loss.

part of T69526