I think that, assuming this is sound, it would be worth including this operation in the standard library.
This is because the question has come up several times, and whenever it does, there's always a discussion of soundness and how best to implement it. A documented function would clarify the matter.
(It might also help steer people away from the variation that can't (?) be done soundly w.r.t. provenance, where instead of finding a slice in a larger slice, one attempts to "concatenate" two slices if they are determined to be adjacent in memory. Or, maybe there's even a way to do that with compiler support.)