NuGet: Store source links

Some NuGet packages provide a commit id next to the origin URL where their code can be found, for example:

https://forge.softwareheritage.org/source/swh-lister/browse/master/swh/lister/nuget/tests/data/https_api.nuget.org/v3-flatcontainer_sil.core.desktop_10.0.1-beta0012_sil.core.desktop.nuspec;05cd1de1cde7ed26ca46d970e4635ba142af9031$24

This is called Source Links

In short, they are very valuable, because they allow debugging through dependencies (akin to debug symbols in C), and it is the only way to match version numbers in the Nuget registry with git commits

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Migrated from T4623 (view on Phabricator)