Many projects in Arcade are currently targeting .NET Core 2.1, which then required a downgrade of libraries per #6738 (comment). We should upgrade all projects to at the minimum use .NET Core 3.1 (upgrading to 5.0 would be ideal).

• Upgrade Arcade projects to support .NET Core 3.1 at a minimum. .NET 5 would be ideal.
• Upgrade the Dependency Injection (and related) libraries back to at least 3.1.9. (Abstractions, Logging)