Adjust LOD selection metrics to use attribute error

- Revert meshoptimizer patch; the metric used for LOD selection now
incorporates attribute error
- Since LOD selection is now aware of attribute deviation, we don't
need to use a higher normal weight
- To prevent normal creases from creating input triangles with very
large normal deviation, reduce default normal merge threshold
- Since we now use combined metric to select LODs, we never need LODs
with error>1 as these should not be selected if the mesh is visible.

thirdparty/meshoptimizer/simplifier.cpp

@@ -2048,7 +2048,7 @@ size_t meshopt_simplifyEdge(unsigned int* destination, const unsigned int* indic
 
 	// result_error is quadratic; we need to remap it back to linear
 	if (out_result_error)
-		*out_result_error = sqrtf(vertex_error) * error_scale;
+		*out_result_error = sqrtf(result_error) * error_scale;
 
 	return result_count;
 }