Fix some TensorPrimitives tests failing for me locally with checked builds (#101745)

This is just:
- Adding tolerance checks for NFloat that are the same as for float/double
- Adding tolerance for MultiplyAddEstimate that matches our other tolerances for "Estimate" functions

This addresses everything failing for me locally, but it doesn't match the failure spike recently highlighted in CI.

Author: stephentoub

src/libraries/System.Numerics.Tensors/tests/Helpers.cs

@@ -3,6 +3,7 @@
 
 using System.Collections.Generic;
 using System.Linq;
+using System.Runtime.InteropServices;
 
 namespace System.Numerics.Tensors.Tests
 {
@@ -72,8 +73,18 @@ public static bool IsEqualWithTolerance(float expected, float actual, float? tol
             {
                 return (T?)(object)halfTolerance;
             }
+            else if (typeof(T) == typeof(NFloat))
+            {
+                if (IntPtr.Size == 8 && doubleTolerance != null)
+                {
+                    return (T?)(object)(NFloat)doubleTolerance;
+                }
+                else if (IntPtr.Size == 4 && floatTolerance != null)
+                {
+                    return (T?)(object)(NFloat)doubleTolerance;
+                }
+            }
 #endif
-
             return null;
         }
     }