Refs. swh/infra/sysadm-environment#5608

Refs. swh/infra/sysadm-environment#5608

Refs. swh/infra/sysadm-environment#5608

Refs. swh/infra/sysadm-environment#5608

We only need the is_skipped and length fields for content nodes
in that use case.

0 is a valid node id and filename id, so it's incorrect to use it as
a special value.

We could use usize::MAX instead, but it's more error-prone (easy to
forget to handle this case) and less idiomatic in Rust.

This also distinguishes the error case (`Err`) and the non-existence case (`None`)

* .label_name() needs to bisect through a large file
* UTF-8 decoding takes a linear time in the file name size
* comparing strings is slower (also linear time) than comparing integers

This requires swh-graph >= 6.7.0, as it fixed a major soundness bug in
label_name_id.

Related to product-management/coarnotify-service#10

- /bchauvet/gitlab_migration/docs/2024.csv
- /bchauvet/gitlab_migration/docs/Roadmap_2024_Q2.xlsx
- /bchauvet/gitlab_migration/docs/rmp.md
- /bchauvet/gitlab_migration/docs/roadmap-2024.rst
- /bchauvet/gitlab_migration/docs/tasks_2024.csv
- /bchauvet/gitlab_migration/old/import.py
- /bchauvet/gitlab_migration/old/roadmap_xls_to_gitlab.py
- /bchauvet/gitlab_migration/old/rollback.py
- /bchauvet/gitlab_migration/.gitignore
- /bchauvet/gitlab_migration/generate_doc_2024.py
- /bchauvet/gitlab_migration/generate_outreach_doc.py
- /bchauvet/gitlab_migration/generate_roadmap_doc_2023.py
- /bchauvet/gitlab_migration/get_summary_csv.py
- /bchauvet/gitlab_migration/hiring_export.py
- /bchauvet/gitlab_migration/roadmap_dashboard.py
- /bchauvet/gitlab_migration/sample-python-gitlab.cfg
- /bchauvet/gitlab_migration/tasks.py
- /bchauvet/gitlab_migration/todo.txt
- /bchauvet/gitlab_tools/sample-python-gitlab.cfg