Configure chronyd to adjust the time smoothly

**What I'd like:**
We need to guarantee that `chronyd` is always running even if the process exits or is killed by the OS. Since `chronyd` could take some time to reconcile the clock (e. g. when the host clock is at January 1 2000), we need to add:

- A `oneshot` service that steps the clock forward aggressively, that runs at boot and never restarts
- A long running service that can be restarted, but smoothly adjusts the clock toward the correct time

Start by locating the existing chronyd configuration and boot service definitions in the repository. Check how services are started and restarted, then verify that the proposed oneshot service runs only at boot while the long-running service can be restarted and adjusts the clock smoothly.

Written by the indexing model from the issue text.