Dangling contents should return a SWHID with no anchor, instead of None

The anchor can be an empty string in case nothing is found. So that fails the
conditional to return None currently and then raises when trying to make a
QualifiedSWHID out of an empty string.

Resolves

```
ValidationError: /api/1/provenance/whereis/{target}/
Invalid SWHID: invalid syntax: %(swhid)s
```

Refs. swh/infra/sysadm-environment#5624

This reduces the wall clock run time from 3 days to 21 hours by evenly
distributing work across threads

Antoine Lambert authored 2 months ago and Antoine Lambert committed 2 months ago

To avoid false positive when running flake8 locally with tox.

Before this commit, the Python code was looking for Rust executables in
swh-graph's executables directory, instead of swh-provenance's

Bump development tools: mypy, codespell, isort, ...

Move all tools configuration in pyproject.toml.

Remove no longer needed mypy overrides.

Update dependencies, imports, and Cargo.toml metadata after swh-provenance-db-build import from swh_graph_provenance

Instead of recomputing a subset of it using a less efficient algorithm, which takes
days to find origins for the last revisions

Include update to `pyo3-0.23.0`