Support collection statistics for expression

[murphyatwork]

Enhancement

Current analyze table can only support collect statistics for raw columns, but not derived expression like analyze table tbl (left(str, 10));

For some particular cases it's crucial:

• The expression can change the data distribution a lot, like left(str, 10), get_json_int(j, '$.clientId')
• The output statistics of this expression cannot be derived from the input, like get_json_int, must have to execute the expression
• UDF functions