Better tracing span (#513)
This will help us get better insight into what is happening and how long
it takes. I'm particularly interested in how long the different source
dist steps take (download, extract, build step(s)), to make better
decisions about their caching, which i want to report through tracing.
Example output:
```console
$ RUST_LOG=puffin=info cargo run --bin puffin -q -- pip-compile -v --no-cache scripts/requirements/all-kinds.in > /dev/null
puffin_distribution::source_dist::download_source_dist filename="werkzeug-3.0.1.tar.gz", source_dist=werkzeug @ ff1904eb5e/werkzeug-3.0.1.tar.gz
puffin_dispatch::build_source source_dist="werkzeug @ ff1904eb5e/werkzeug-3.0.1.tar.gz", subdirectory=None
puffin_build::extract_archive sdist="werkzeug-3.0.1.tar.gz"
puffin_dispatch::resolve requirements="flit-core <4"
puffin_dispatch::install requirements="flit-core ==3.9.0", venv="/tmp/.tmpgZAEAh/.venv"
puffin_build::get_requires_for_build_wheel name="build_wheel", python_version=3.12
puffin_build::build package_id="werkzeug @ ff1904eb5e/werkzeug-3.0.1.tar.gz"
puffin_build::run_python_script name="build_wheel", python_version=3.12
puffin_dispatch::build_source source_dist="pydantic-extra-types @ git+https://github.com/pydantic/pydantic-extra-types.git@843b753e9e8cb74e83cac55598719b39a4d5ef1f", subdirectory=None
puffin_dispatch::resolve requirements="hatchling"
puffin_dispatch::install requirements="hatchling ==1.18.0, trove-classifiers ==2023.11.22, editables ==0.5, pathspec ==0.11.2, pluggy ==1.3.0, packaging ==23.2", venv="/tmp/.tmpJjweUn/.venv"
puffin_build::get_requires_for_build_wheel name="build_wheel", python_version=3.12
puffin_build::build package_id="pydantic-extra-types @ git+https://github.com/pydantic/pydantic-extra-types.git@843b753e9e8cb74e83cac55598719b39a4d5ef1f"
puffin_build::run_python_script name="build_wheel", python_version=3.12
puffin_distribution::source_dist::download_source_dist filename="django-allauth-0.51.0.tar.gz", source_dist=django-allauth==0.51.0
puffin_dispatch::build_source source_dist="django-allauth==0.51.0", subdirectory=None
puffin_build::extract_archive sdist="django-allauth-0.51.0.tar.gz"
puffin_dispatch::resolve requirements="wheel, setuptools, pip"
puffin_dispatch::install requirements="setuptools ==69.0.2, pip ==23.3.1, wheel ==0.42.0", venv="/tmp/.tmplSZisu/.venv"
puffin_build::build package_id="django-allauth==0.51.0"
Resolved 35 packages in 11.71s
```
2539f00952