[Feature] add nint IntPtr derivatives among the argument formatters

[mwpowellhtx]

As in the assert TypeMappings, also documented among Characteristics of the integral types, i.e.

// List of intrinsic types => C# type names
static readonly Dictionary<TypeInfo, string> TypeMappings = new Dictionary<TypeInfo, string>
{
    //...
    { typeof(nint).GetTypeInfo(), "nint" },
    { typeof(nuint).GetTypeInfo(), "nuint" },
    // ...
};

I think nint and nuint are somewhat new integral types, but could not tell you exactly when they were added.

For sake of completeness.

[bradwilson]

The underlying types themselves are not new (IntPtr and UIntPtr date back to .NET Framework 1.1 in 2003), but the aliases are, and they require C# 9 (released in 2020). It's a compiler feature rather than a runtime feature since they're just type aliases.

[bradwilson]

Available in v2 2.7.1-pre.12
Available in v3 0.1.1-pre.390

https://xunit.net/docs/using-ci-builds