Improve Release Promotion Process

For the LTS 2023 and next ones we want to improve some part of our release promotion process.

First, we want to have a proper Github release created for each promoted release here: https://github.com/nuxeo/nuxeo-lts/releases
This GitHub release will allow us to list useful things of the promoted release such as the build version promoted, links to the ZIP distribution / Docker image, release and upgrade notes, ...

To allow people to easily know vulnerabilities issues still present on a promoted release, we want to store the Grype scan outputs (bare Nuxeo Docker image and with all packages?) as assets on the GitHub release.