QOL update to the PerResidueEsmProbabilitiesMetric (#26)
This short PR:
* Adds the proper citation for ESM
* Adds some checks for NaNs/Infs to the Perplexity/softmax calculation
* fixes a typo in MIFST.cc
* Prevents an error in SampleSequenceFromProbabilities when calling the SimpleThreadingMover without mutations
* Fixes const behavior in SampleSequenceFromProbabilities
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Co-authored-by: moritzertelt <moritz.ertelt@gmail.com>