[FEATURE] Enhance `dedup` PPL command with `sortby` option

[ykmr1224]

Add sortby option to dedup PPL command to make it easy to sort the result.
When sortby option is specified, the input rows should be sorted before dedup. (equivalent to put sort command before dedup command)

Syntax:
dedup ...(other params) <sort-by-clause>

<sort-by-clause>
Syntax: sortby ( - | + ) <sort-field> [(- | +) <sort_field> ...]

Example:
dedup user sortby -_time

Priority: Low (Expecting lower usage and can be done with separate sort command)