Concat function supports 0 or 1 parameter

Design

Kylin5 currently does not support UDFs with only one parameter. However, Spark and Hive do support it. Additionally, it has been verified that Spark and Hive also support concat with zero parameters. Here, we are adding support for Kylin5 to handle both zero and one parameter cases.

Kylin5当前自定义的 udf 不支持一个参数的。但是 spark 和 hive 支持。同时还验证了一下 spark 和 hive 还支持 concat 为0 个参数的情况。这里对增加Kylin5对0个和1个参数的支持。