Following the pattern set up by Martin and Lucas for similar PRs. Can be
reviewed by commits:
1. move scep directory into monorepo
2. update import paths
3. update go.mod, go.sum
4. fix golint errors in scep package
5. skip a failing test that's been broken for a while
6. fix that failing test
# Checklist for submitter
If some of the following don't apply, delete the relevant line.
<!-- Note that API documentation changes are now addressed by the
product design team. -->
- [x] Manual QA for all new/changed functionality
Also verified that our test suite runs the `scep` tests.
