implementing a new assertion test for the Gaintemplate fitting

[giuspugl]

this PR addresses the issues #613.

[giuspugl]

at the moment the test doesn't pass, mainly because :

• an error on the size of the fitted gain_amplitudes calibration.template_matrix.templates[0].data['Calibrate_solve_amplitudes'] instance of https://github.com/hpc4cmb/toast/blob/44d9f84ecc28752de2028cf3f402891ba34a1049/src/toast/ops/mapmaker_templates.py#L33 (should be n_observations * n_detectors * n_polyorders instead there is an extra list of zeros )
• calibration.template_matrix.templates[0].data['temp_LHS'] has only data from 1 detector (am running the test serially )
• why does calibration.template_matrix.templates[0].data['temp_LHS'] have 1/K units ?