Feature Request: support deploying the charm on arm64 machines

We (the HPC team) are currently investigating blockers for arm64 support on Charmed HPC and the Slurm charms, but while investigating Microceph (which we use for our HA testing on slurmctld), we noticed it doesn't publish builds for arm64 yet. @dsloanm noticed this comment on the `charmcraft.yaml`:

https://github.com/canonical/charm-microceph/blob/2c06a52c401cdfa3c8685c4613a26ee061d61d2a/charmcraft.yaml#L6-L11

So it might just be adding the proper CI to publish arm64 builds? Since the Microceph snap already does support arm64 and everything.
We could also use the standalone Ceph charms, but we would strongly prefer using the Microceph charm to avoid the increased deployment complexity of this path.

Start with charmcraft.yaml, especially the lines linked in the issue, and inspect the repository's existing CI configuration for how builds are published. Done means the Microceph charm publishes an arm64 build using the existing arm64-capable snap and can be deployed on an arm64 machine.

Written by the indexing model from the issue text.