Schedule nightly system SSL builds for testing

Related to #6319 (closed).

Summary

Prior to enabling system ssl builds by default for our end-users, we want to have lots of opportunity to test these changes.

  • Let's start running a nightly build that uses the system ssl packages for others to use for testing, and to ensure we keep them building
  • Let's start running a nightly trigger build of ubuntu using systemssl to run through the QA tests