Report encryption support before first attempt

MicroCeph supports OSD encryption with the `--encrypt` flag. In order for this to work, a user must first run the following before adding the disks they want.
```bash
sudo snap connect microceph:dm-crypt
sudo snap restart microceph.daemon
```

However, in practice you are only informed of the current status if you manually attempt to add a disk. If the above connection hasn't been established, MicroCeph returns an error informing you to run those commands and try again.

This poses a particular issue for MicroCloud because we can't view MicroCeph's snap connections. Instead after the clusters have been formed and the disks are being created, the whole initialization breaks because the connection was not established beforehand.

It would be convenient if this information could be included in `microceph status` with a line similar to `encryption: enabled/disabled`. That way in MicroCloud we can detect ahead of time if the connection has been made by checking against the MicroCeph API. Then we can either prompt the user to enable encryption per OSD or warn them that encryption is not enabled across their snaps.

Not a blocker for the LTS, but would be nice to include in a coming point release.