Add .NET 7 target, update dependencies, run tests on all supported target monikers

[mlaily]

Warning: the test verifying that method names are resolved doesn't work on .NET 7.

I'm not sure whether it's an actual problem with fasmi, or if the implementation of the tested method simply changed in .NET 7...

I'm not sure what's the correct fix...

EDIT: I did a few other tests, and it seems like the .NET 7 version fails to resolve most if not all method names for methods defined outside the source project.