Update drive-mixer calibration AWG channel dependency

[MiniSean]

Source of the problem:

• Currently, the drive mixer calibration depends on a HAL_Transmon parameter (mw_awg_ch) to specify which AWG channel offsets to vary during offset-calibration. This is confusing since the AWG drive channels are specified in the lutman linked to the HAL_Transmon.

How to solve:

• Update mixer calibration functions to access the HAL_Transmon microwave lutman and access the specific channel there.