get_det_bias_flags should also check for tau_eff nans

[aashrita]

I notice nans come through after the updated tau_eff calculations in sodetlib, probably from poor bias step fits for particular detectors. This can interrupt mapmaking, and a more efficient way of handling this might be get_det_bias_flags function handling this:

sotodlib/sotodlib/tod_ops/flags.py

Line 18 in b3efc0c

def get_det_bias_flags(aman, detcal=None, rfrac_range=(0.1, 0.7),

[msilvafe]

This function was added to address that issue:

sotodlib/sotodlib/preprocess/processes.py

Lines 1996 to 2006 in 6216103

	class DetcalNanCuts(_Preprocess):
	"""
	Remove detectors with NaN values in the specified det_cal metadata fields.
	Example config file entry::
	- name: "detcal_nan_cuts"
	select:
	fields: [tau_eff, phase_to_pW]
	"""
	name = 'detcal_nan_cuts'

[aashrita]

For quick scripting, it would be useful if the logic there was available in a flagging function that preprocess calls like many of the other flagging in preprocess. Else I can only use this if I set up things exactly for preprocess with contexts etc, and I often am not doing that.