lfs: convert to using exthelper to wrap functions I'm not 100% sure that upgraderequirements() can be double annotated safely, but it seems OK based on printing the address of the function being wrapped. One thing I've noticed is that @eh.reposetup doesn't do the usual check to ensure that it's a local repo. Should that be baked into @eh.reposetup() somehow, possibly with a non-default option to skip the check? It seems like a gaping hole if every function that gets registered needs to add this check.

tests: convert a test extension to use exthelper This provides test coverage to uipopulate().