Blender Git Loki

Geometry Nodes: Remove experimental option for fields

This enables fields as the official workflow for geometry nodes.
While many features are converted to use fields rather than the old
attribute workflow, many are not yet converted. In that case, the
unconverted nodes are still accessible with an experimental option.
In the coming weeks the rest of the nodes will be converted.

Differential Revision: https://developer.blender.org/D12672