[BUG] Unmanaged memory leaks

[MichaelGrafnetter]

Describe the bug

Greetings, @GuyTe! While implementing a similar functionality in my own project, I noticed that your code does not properly release unmanaged memory pointers returned by the GenerateKDFContext function through the out IntPtr outContext parameter in KdsCli.cs

Expected behavior
Unmanaged memory allocated by the GenerateKDFContext call should be released by the undocumented SIDKeyProvFree native function. If interested, feel free to copy my own implementation of the SafeSidKeyProviderHandle wrapper, which makes sure that the unmanaged memory is released under any circumstances.