Expand `OutString` to support `ToString` and others

[thorium-cfx]

Goal

Several usability functions for the OutString type, allowing it to be used directly without explicit conversion. See API proposal for examples.

Importancy

Quality of Life (QoL)

API and/or potential implementation

Debug.WriteLine(myOutString);
Debug.WriteLine($"{myOutString}");
Debug.WriteLine("mystring" + myOutString);

myOutString.ToString();
myOutString.ToCString();

myOutString.SubString();
myOutString.SubCString();

Extra

No response