* add the array_distinct function
* add the support for decimal and update variable names
* add docs and regression test for array_distinct function
Co-authored-by: hucheng01 <hucheng01@baidu.com>
FEFunctionSignature do not support ArrayType as args, then following SQL failed:
`> select array_contains([1,2,3], 1);`
ERROR 1105 (HY000): errCode = 2, detailMessage = Unexpected exception: org.apache.doris.catalog.ArrayType cannot be cast to org.apache.doris.catalog.ScalarType