DM-26119 I learned that when pipetask uses multiprocessing we never instantiate an Instrument and therefore we never define the filters for that instrument in the global singleton.
In single process mode it's fine because at some point an Instrument is created.
Modify pipetask multiprocessing such that the dataIds are scanned for the "instrument" dimension and we call Instrument.fromName(dataId["instrument"], registry). Currently we only expect one instrument.
When the singleton is removed it's likely that some related initialization will be needed to register the filters but we assume that would allow the same initialization for multiple instruments.