Replace Test and push for LTS 2019 QA platform build

As the LTS 2019 will be supported until 2023, it is worth getting rid of the current QA platform to validate the LTS 20219 pull requests and migrate it to the our Jenkins CI platform. This will allow us to have a faster feedback loop with Github checks, an unified way for developers to validate pull requests on LTS 2019 and LTS 2021 and the full control of the CI build/platform.

Let's create in the Platform Jenkins a multibranch pipeline on nuxeo/nuxeo, building the PR-* branches that target the 10.10 branch, running the equivalent of the current 10.10 T&P job in qa2 and setting GitHub statuses on the 10.10 PRs.

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New job https://jenkins.platform.dev.nuxeo.com/job/nuxeo/job/10.10/job/nuxeo/
4 GitHub status checks on the PRs:

Note that the build is longer than the T&P (~ 4h30 vs 3h30), certainly due to recurrent (and slower) Maven artifact download from packages.nuxeo.com.