Geometry Nodes : Removing "Combine Strings" and Group Instance ID from UI
This diff remove "Combine Strings" and "Group Instance ID" nodes from the UI (but keep them in the source code to be able to bring them back if needed).
This introduces a regression. Users need to re-create their modifiers and set their values again. The NodeGroups are intact so all they need is to create new "Empty" modifiers and set the node group.
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Original problem: Eventually most modifiers will be node-based, so naming this new modifier "Nodes" will get outdated pretty quickly.
Calling it "Empty" it's fairly descriptive, since the node tree simply connects the modifier Input to an Output, without any effect.
There is a potential problem, that it could be associated with the Empty object type. Like some sort of Hook.
This is the task T82700, and the design task T82537.
Geometry Nodes: use density attribute name instead of index as node input
This implements a workaround for the issue that (for historical reasons) the names of vertex groups are stored on the object while the actual vertex group data is stored on the mesh.
The solution is to copy the vertex group names from the object into the `MeshComponent` so that the information is not lost, when the object cannot be accessed.
Previously, the execution function of a geometry node has three parameters. Now it has only one. This makes it easier to pass more information to the execution function, that might only be used by a few nodes, because we don't have to add more parameters that are unused in most cases.