Mostly to take advantage of the performance improvments

Related to infra/sysadm-environment#4626
Related to infra/sysadm-environment#4625

This sent celery events at the end of the ingestion which is not required. It's no
longer relevant for the current scheduling management. It's an initial typo when
migrating those workers.

Related to T4540

Related to T4540

Related to T4540

Related to T4517

This deals with package loaders only: pypi, npm, maven, opam, ...

Related to T4144

Related to T4144

Related to T4144

Local run on my machine does not work properly. This generates pkg-resources==0.0.0 and
probably some other irrelevant things.

So, instead, I used docker:

```
$ docker run -ti -v $PWD:/src -u root --entrypoint=bash python:3.9
```

In another shell:

```
$ docker exec --user 1000 \
  $container_name /src/scripts/generate-frozen-requirements swh-graphql
...
```
- $container_name is derived out of `docker ps`.
- uid 1000 is derived out of your `id $USER`

Related to T4464

Related to T4134

Related to T4131