Add parameter `chunksize` to `DbToDbOperator`

[augusto-herrmann]

The DbToDbHook has a chunksize parameter:

FastETL/fastetl/hooks/db_to_db_hook.py

Line 31 in d82c5c4

chunksize: int = 1000,

But the DbToDbOperator does not:

FastETL/fastetl/operators/db_to_csv_operator.py

Line 37 in d82c5c4

def __init__(self,

So it is not currently possible to define a chunk size in a DAG using the operator.

A chunksize argument to the operator so that it can be used. The code should pass it on to the hook if used.