fix(cluster): crash while create rollup sma

fix(os): getline memory free error.

refactor(cluster): make the comment and code of udf to variable length

add between python case

enh: support variables like $data[0][1] and $data(db)[0] in tsim scripts

feat: block-wise sma integrate

enh(query): set the parameters for system database to be NULL

fix(query): translate var type from value node to SVariant should include var header

ehn(query): set the parameters for system database to be NULL by default when responsing "show databases" command.

fix(query): fix bug in calculating the aggregate function

fix(query): fix bug in calculating the aggregate function with constant numeric value as input parameter.