[Improve]: scan operations for IReadOnlyStoreView and fix of Find with all 0xff keyPrefix

tests/Neo.UnitTests/Extensions/UT_ReadOnlyViewExtension.cs

@@ -112,7 +112,7 @@ public void TestFindEmptyPrefix()
             action.Should().Throw<ArgumentException>();
 
             action = () => dataCache.Find([0xff], SeekDirection.Backward).ToArray();
-            action.Should().Throw<ArgumentException>();
+            action.Should().Throw<NotSupportedException>();
         }
     }
 }