Updating Nitric

[raksiv]

When updating nitric, unused membranes should be pruned and the relevant version should be pulled.

Options -

nitric doctor
We could internally run:

docker pull nitricimages/membrane-local
docker pull nitricimages/membrane-aws
docker pull nitricimages/membrane-gcp
docker pull nitricimages/membrane-do
docker pull nitricimages/membrane-azure

OR (probably better)

We could just prune the contents of the nitricimages repo in the local docker environment, which would force the images to be pulled the next time they're used and avoid pulling images that aren't needed (like clouds that aren't in use)

┆Issue is synchronized with this Jira Story by Unito