spanner: ReadRow() returns not found when there is a column or a struct issue instead of the actual error

[shawncalda-angkas]

When you run the following code

row, err := c.data.Single().ReadRow(ctx, TestTable, spanner.Key{tableID}, []string{"id", "name", "age"})

if there is an issue on the table for example age column is non existing it will also return as "NotFound" and might be confusing that the row corresponding to the primary key is not existing