Convert to use Central Package Management

[lahma]

Now single place to have packages and their versions. See https://devblogs.microsoft.com/nuget/introducing-central-package-management/ for information about the feature.

The versions should be the same as before, didn't include any version updates, but should be easier/clearer in the future after this.

[EdwardCooke]

This is an interesting idea. In the most recently merged PR we cleaned up some unused references, can you rebase?

[lahma]

Rebased, I removed some unnecessary references from projects and also targeted benchmark projects just against net8.0 for easiest dependency resolving. I think it should suffice to benchmark against modern runtime.

[EdwardCooke]

Thanks. However. We do benchmark against net47. I do agree targeting the latest net 80 framework as well.

[lahma]

I restored the net47 target (I think this should ideally be net472 as 4.7.2 is mainstream and comes with the OSs).