Blender Git Loki

Geometry Nodes: Expose texture and material inputs to modifier

This allows choosing material and texture sockets for the group input
node in the modifier. Note that currently grease pencil materials are
displayed in the list, even though grease pencil data is not supported
yet by geometry nodes. That is more complicated to fix in this case,
since we use IDProperties to store the dynamic exposed inputs.

Differential Revision: https://developer.blender.org/D11393