CI Pipelines to build and promote LTS 2021 HF

We need at least:

• A build pipeline to continuously build the hotifx package for a given nuxeo build version, e.g. 2021.2.21, making the diff with the previous release, e.g. 2021.1. This job will be triggered by the nuxeo-lts build pipeline. It will build a ZIP package and deploy it to an internal Maven registry, as well as a Docker image built from the LTS (2021.1) and having the built hotifx package installed, automatically pulling the previous hotfixes at installation. This Docker image will be used for internal validation of an LTS installation + hotfixes in a QA environment.
• A release pipeline to deploy a candidate hotfix package from the internal Maven registry to Connect prod.