Outsource Windows API definitions (extern) to CsWin32

[YoshiRulz]

https://github.com/microsoft/CsWin32

Pre-merge checklist:

• All features working
• Evaluate whether MotW zapper can be removed, per BizHawk won't start on Windows 10. #1892 (comment)
• Removed all externs everything that's compatible with AnyCPU
• Removed as many constants and enum definitions as possible
• Double-checked doc comments on manual overloads in Bizware.Externs
• Move method signature changes to separate commit
• Move whitespace, reflow, etc. to separate commit
• Update Nix NuGet lockfile
• look at https://learn.microsoft.com/en-us/dotnet/standard/native-interop/disabled-marshalling
• try w/ Multi-target .NET Framework 4.8 and .NET 8 #3745

[YoshiRulz]

Struggling w/ AVI, namely this array cast:

BizHawk/src/BizHawk.Bizware.Externs/AVIFIL32.dll.cs

Lines 9 to 15 in cc7ff7b

	public static unsafe nint AVISaveOptions(IAVIStream[] ppavi, ref AVICOMPRESSOPTIONS opts, HWND owner)
	{
	fixed (AVICOMPRESSOPTIONS* popts = &opts)
	{
	return AVISaveOptions(owner, uiFlags: 0, nStreams: 1, ppavi, &popts);
	}
	}

BizHawk/src/BizHawk.Client.EmuHawk/AVOut/AviWriter.cs

Lines 632 to 633 in cc7ff7b

	public static unsafe int AVISaveOptions(IntPtr stream, ref AVICOMPRESSOPTIONS opts, IntPtr owner)
	=> unchecked((int) AVIWriterImports.AVISaveOptions((IAVIStream[]) (void*) stream, ref opts, new(owner)));

(was:)

BizHawk/src/BizHawk.Client.EmuHawk/AVOut/AviWriter.cs

Lines 627 to 636 in fe3d45b

	private static unsafe int AVISaveOptions(IntPtr stream, ref AVIWriterImports.AVICOMPRESSOPTIONS opts, IntPtr owner)
	{
	fixed (AVIWriterImports.AVICOMPRESSOPTIONS* _popts = &opts)
	{
	var pStream = &stream;
	var popts = _popts;
	var ppopts = &popts;
	return AVIWriterImports.AVISaveOptions(owner, 0, 1, pStream, ppopts);
	}
	}

[kalimag]

BizHawk/src/BizHawk.Client.EmuHawk/AVOut/AviWriter.cs

Lines 632 to 633 in cc7ff7b

	public static unsafe int AVISaveOptions(IntPtr stream, ref AVICOMPRESSOPTIONS opts, IntPtr owner)
	=> unchecked((int) AVIWriterImports.AVISaveOptions((IAVIStream[]) (void*) stream, ref opts, new(owner)));

Presumably that should be new [] { stream }? stream is a pointer to a single stream, and AVISaveOptions expects a pointer to an array of pointers. But it also requires changing from raw IntPtrs to the generated IAVI* types all the way up the chain.