Move which_in_eml to ropensci/EML

[dmullen17]

@maier-m I'm cleaning up datamgmt and this function makes way more sense in EML. Did you ever ask if Karl wanted to add it to the ropensci/EML package?

If you're interested in the longer story: I used which_in_eml as a helper in this function NCEAS/arcticdatautils#97, but because datamgmt already imports arcticdatautils then arcticdatautils cannot import any datamgmt functions because this creates a cyclic package dependency. My hacky solution was to add which_in_eml to arcticdatautils so I could use it 🙄, but it makes way more sense in EML.

[maier-m]

Yeah, you could try to move it to EML... I think most the devel is being done on eml2 though and may be better to port there with some small code mods. Not entirely sure though, I never asked.