charmcraft upload should allow a user to also release the charm

[lucabello]

What needs to get done

Currently, to release a charm you have to:

charmcraft upload <.charm>  # note down the revision number
charmcraft upload-resource <resource>  # note down the revision number
charmcraft release ...

We should have a way to release a charm right after uploading it; the resource can be uploaded automatically according to the upstream-image field in charmcraft.yaml.

The approached discussed with @lengau would be to add --release=latest/edge flag to the upload command. Another option could be to introduce a new command that does both the update and release together.

An example would be something like:

`charmcraft upload prometheus.charm prometheus-k8s --resource=prometheus-image:ubuntu/prometheus:9 --release=latest/edge`

Why it needs to get done

In CI, releasing a charm currently translates to those three commands with weird parsing of the revision numbers, and the manual process is extremely error-prone.