Removing overly restrictive version cap on Microsoft.Extensions packages

[rwkarg]

Version 6.0.0 of the Microsoft.Extensions.** packages all support netstandard2.0 so can be used all the way back to netcoreapp2.1.

This is causing issues where some apps that are still on netcoreapp3.1 are using another package that requires Microsoft.Extensions.Logging.Console 5.0.0+ which references Microsoft.Extensions.DependencyInjection.Abstractions 5.0.0. But this package has a requirement of <4.0.0 for M.E.DI.A (despite the fact that there is nothing otherwise that would prevent 5.0.0+ from being used).

Note that this won't change the version used for any existing usages. It will only allow other use cases to opt in to reference a higher version.