The optional NuGet packages should enforce version constraints

[PathogenDavid]

It isn't supported to mix different versions of the various Mochi.PhysX NuGet packages, but NuGet won't enforce this for the optional packages (such as the checked variant of the runtime.)

We should enforce this at compile time using a method similar to the one used for ClangSharp.Pathogen.

We might consider also doing something similar at runtime via https://github.com/MochiLibraries/Mochi.PhysX/issues/6.