qe: add private method _upload_first_sequence
qe: add private method _upload_first_sequence

Is called in _configure_mc case the sweep_func_1st_dim does not take care
of the sequence upload. The method is meant to be overwriten by child classes
for the non standard case first sequence != self.sequences[0].

(cherry picked from commit 8229333a9b276e5c01b8e451293cc59c529836f5)

QudevETH/PycQED_py3