Use HashCode.AddBytes in CodeHeaderValue.GetHashCode

Author: stephentoub

src/libraries/System.Security.Cryptography.Cose/src/System/Security/Cryptography/Cose/CoseHeaderValue.cs

@@ -261,10 +261,14 @@ public int GetValueAsBytes(Span<byte> destination)
         public override int GetHashCode()
         {
             HashCode hashCode = default;
+#if NET
+            hashCode.AddBytes(EncodedValue.Span);
+#else
             foreach (byte b in EncodedValue.Span)
             {
                 hashCode.Add(b);
             }
+#endif
             return hashCode.ToHashCode();
         }