bifrost_infer_snapname_here

PlasmaCalcs.hookups.bifrost.bifrost_io_tools.bifrost_infer_snapname_here(dir='.')

infer snapname based on files in directory, if possible.

For files like snapname_NNN.idl, if all have same snapname, return it.
If no such files, raise FileNotFoundError; if multiple implied snapnames, raise FileAmbiguityError.
NNN can be any integer, doesn’t need to be 3 digits.