Import DM-35718 solution for Gen2 datasetExists of bypass data

DM-35718 ("bypass functions do not play well with datasetExists (in gen2)") fixes a Gen2 butler bug. This fix is essential for our processing of NIR PFSB files. Since the Gen2 middleware has been deprecated (and in many instances, completely removed) by LSST, this fix will not be released by them, and so we need to get it ourselves.

This might be done either by installing the daf_persistence branch with the fix or by monkey-patching the butler. The former solution might cause problems with the eups dependencies, so we'll try the latter solution.