[rustbuild] ignore single tests

[davidak]

I'm packaging a rust program for the Nix package manager. We build packages in a sandboxed environment to not rely on external state and have reproducible builds.

Now a test fail because it want's to use the network. I want to disable this one test with a commandline parameter.

Tests could also be grouped (#35678), so i can disable all tests that need network like --test offline, but a simple list like --test --disable-tests test_update_cache,test_missing_cache would do it for now.

[jyn514]

We'd want to implement this with --exclude, so I'm going to close this as a duplicate of #96342. I don't think we use any tests today that require network access, please open a new issue if that's not the case :)