Related to blender/blender#108534
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Folks keep running into this it seems so I put the PR together to get things moving.
There looks to be 2 limits but one of them seems a bit broken.
```
/* Hardware limit is 16. Position attribute is always needed so we reduce to 15.
* This makes sure the GPUVertexFormat name buffer does not overflow. */
#define GPU_MAX_ATTR 15
/* Determined by the maximum uniform buffer size divided by chunk size. */
#define GPU_MAX_UNIFORM_ATTR 8
```
The first, from an empirical test seems to indicate 14 useful Geometry Node attributes before the shader "breaks". Are we off by one somewhere?
The second, from blender/blender#117967, seems to be used when Custom Object Properties are set.
