The subversion loader now includes a C++ extension module so only generate
source distribution for PyPI upload as the binary wheel needs to be generated
on a dedicated docker image then repaired with the auditwheel tool.

So until our Jenkins pipeline supports building and repairing binary wheels
for linux platform, disable the binary wheel generation for swh-loader-svn.

Since recently, merge requests are not rebuilt by Jenkins when pushing
new commits to it. This could be related to some default configuration
changes in latest release of GitLab plugin for Jenkins.

As that behavior is not enabled by default in gitlab trigger settings
explicitly enable it in jenkins jobs configuration.

See https://storyboard.openstack.org/#!/story/2010752

The tests for swh-webhooks rely on docker-compose and currently cannot
be executed by multiple jobs in parallel due to the way our jenkins
pipelines are configured.

So ensure only one job can be executed at a time to avoid race conditions.

More efficient in regards to our current way of building some specific images which are
growing forever (up until we got no more disk space on thyssen).
That's a simpler workaround than what's discussed in issue [1] [2]. We keep the last "2"
days images so the next build still benefits from it but we drop the rest (so no more
too much disk cost). As this job is triggered daily, that should keep those images in
check.

Provided, the following script is installed on the node:

```
$ root@thyssen:~# cat /usr/local/bin/clean-docker-images.sh

set -x

today=$(date --date '13:00' +%Y%m%d)
yesterday=$(date --date 'yesterday 13:00' +%Y%m%d)

images_to_drop=$(docker image ls \
    | grep -E "softwareheritage/(base|web|replayer)" \
    | grep -v $today \
    | grep -v $yesterday \
    | grep -v "latest")

if [ ! -z "$images_to_drop" ]; then
    echo $images_to_drop \
    | awk '{print $1":"$2}' \
    | xargs docker rmi
fi

docker system prune --filter 'label!=keep' --volumes --force
```

Refs. swh/infra/sysadm-environment#4846

[1] swh/infra/sysadm-environment#4848

[2] swh/infra/sysadm-environment#4846

Previously, we kept them up to 90 days but this quickly eats significant
disk space on the jenkins host as the full HTML documentation for SWH is
published as a report for each build triggered from GitLab.

Related to swh/infra/sysadm-environment#4846

SWH documentations have been merged into a single one so we can now remove
these publish HTML steps.

Refs. swh/infra/sysadm-environment#4766

Refs. swh/infra/sysadm-environment#4766

Refs. swh/infra/sysadm-environment#4766

Related to swh/devel/swh-web#4734

It enables a better selection of the git branch to checkout when
dealing with gilab merge requests.

It enables to test proper build of docker images when their dockerfiles
are modified without impacting the images used by our Jenkins jobs.

This also adapts to use the proper check as the previous check implemented always
returned false (without an absolute path that is).

Refs. swh/infra/sysadm-environment#4524

Refs. swh/infra/sysadm-environment#4524

Some apps do not declare theirs just yet. We want to update their frozen dependency sets
the same way nonetheless.

Refs. swh/infra/sysadm-environment#4524

To the minimum. That will ease output reading while still having enough context to know
when the repository is at.

Refs. swh/infra/sysadm-environment#4524

That would ease triggering back another job (to the expanse of creating more tags on the
same commit which should be fine).

Refs. swh/infra/sysadm-environment#4524

Refs. swh/infra/sysadm-environment#4524

Refs. swh/infra/sysadm-environment#4524

True by default to alway clean up built docker image. This can be switched off to ease
debugging without losing too much time waiting for a docker image rebuild.

Refs. swh/infra/sysadm-environment#4524

This also adds a DRY_RUN flag to the job to allow dry run build.

Refs. swh/infra/sysadm-environment#4524

Refs. swh/infra/sysadm-environment#4524

Given an application name, this triggers in that order:
- a generation of a new frozen set dependency for that application
- a docker image with that frozen set
- then pushes the resulting docker image to the gitlab registry
- finally this cleans up the workspace and the docker image built

Ref. swh/infra/sysadm-environment#4724

When a Jenkins build for a merge request ends, add a comment to the merge
request with the build status and a link to the Jenkins job.

Target branch is ususally master for a merge request so such builds
were no longer triggered.

Use {%- instead of {% as the former eats previous whitespaces.

For trying our some docker jobs within it.

Ref. swh/infra/sysadm-environment#4724

With the lts, that would not install the plugins from the txt file.

Ref. swh/infra/sysadm-environment#4724

Ref. swh/infra/sysadm-environment#4724