Solution Files in libraries don't list all required dependencies

[ViktorHofer]

Our solution files aren't up-to-date and need dependencies added to them (ie System.Runtime.CompilerServices.Unsafe). Currently most of the builds fail because of the missing Unsafe dependency which TestUtilities relies on.

The plan is to use slngen to keep the solution files up-to-date and ideally protect this in CI. To fix the build issues I will send a PR to do a manual update.

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