.NET 8 optimisations and build warnings.

[TheNewAutonomy]

Catalyst's .NET 8 branch now has no build errors but has many build warnings, mostly in relation to coding standard changes since .NET Core 3.0.

Time needs to be taken to go through these build warnings and to resolve as many as practically possible. Ideally we would get to a point that we can set Warnings as Errors in the compiler. However, warnings frequently arise in any project and so this would only happen when there's a team in place to support build warnings.