Linux compatibility

[BinToss]

See HaloSPV3/Gemini#54 for planning and discussion.

KEY ISSUES

Native Interop

More often than not, this involves DllImport attribute on functions/methods marked with the extern keyword.
Wherever we call one of these methods, the caller should wrap this in a try-catch statement.
https://stackoverflow.com/a/970134/14894786

HXE.HCE.Registry

This class is used to discover an existing ProductID of either Retail (halo) or Custom Edition (haloce). If one if found, we use the same patch Chimera uses to skip redundant product activation checks when the game runs.

HXE/src/HCE/Registry.cs

Lines 109 to 146 in d1b27dc

	public static bool GameActivated(Game game)
	{
	/** Select a registry subkey based on the Game parameter */
	string subkey;
	switch (game)
	{
	case Game.Retail:
	subkey = Path.Combine(WoWCheck(), Retail);
	break;
	case Game.Custom:
	subkey = Path.Combine(WoWCheck(), Custom);
	break;
	default:
	throw new ArgumentException("The specified game does not need activation.");
	}
	/** Open the subkey and read the PID entry */
	bool keyIsValid;
	bool subkeyIsValid = false;
	try
	{
	RegistryKey key = WinReg.LocalMachine.OpenSubKey(subkey);
	keyIsValid = key != null;
	if (keyIsValid)
	subkeyIsValid = !string.IsNullOrEmpty(key.GetValue("PID").ToString());
	}
	catch (Exception e)
	{
	var file = (File) Paths.Exception;
	file.AppendAllText($"Error -- {e}");
	throw;
	}
	return keyIsValid && subkeyIsValid;
	}

GUI windows

• Settings
• Positions
  Both of these windows use WPF which is Windows-only. This dependency could be replaced with UNO, Blazor (web app) or MAUI (not Linux-compatible) more easily than in the case of SPV3-Loader.

Runtime-Specific AppHosts

This is going to be interesting (read as 'aggravating') depending on whether we compile for Windows with some compatibility logic or compile separate apps for Windows and Linux hosts.

If we compile separate apps for each platform/runtime, there will be one less headache to deal with.
Otherwise, we'll have to work around Runtime and OS behavior being unexpectedly different from DotNet on Windows.

In either case, we will need to introduce platform-specific code paths.

I hope HXE.SFX won't become an issue...