Resurrect fake daq, fix DAQReader time conversion
Created by: JelleAalbers
This resurrects the fake_daq script, used to mimic the DAQ on a regular computer. You must point it to a folder with raw_records
data and tell it which run to read; it will then create "live records", if desired at a specific write rate.
Perhaps more importantly, this fixes a bug in the DAQReader's absolute time conversion (https://github.com/XENONnT/straxen/issues/17). A bare 1e9 was used, but that gives a float. Our times are 64-bit integers, so doing float math with them leads to inaccuracies. In this case, it led to records with fractional-sample times, which caused strange crashes later in strax.
(I also remove some unused old straxen contexts)