Repack netstandard facade in ckan.exe

[HebaruSan]

Problem

The metadata tester crashed on KSP-CKAN/NetKAN#9917 despite its changes being simple and trivially correct:

https://github.com/KSP-CKAN/NetKAN/actions/runs/7749494610/job/21134148266

FATAL UNHANDLED EXCEPTION: System.TypeLoadException: Could not load type of field 'CKAN.SteamLibrary+<>c__DisplayClass0_0:txtParser' (0) due to: Could not load file or assembly 'netstandard, Version=2.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51' or one of its dependencies.

Cause

As of #4010, we now reference ValveKeyValue, which is a netstandard2.0 library. Repacking it requires resolving a reference to netstandard.dll, which I accomplished by adding _build/lib/nuget/netstandard.library/2.0.0/build/netstandard2.0/ref/ to ILRepack's Libs argument, since a copy of netstandard.dll is placed there by Nuget during restore.

The result of this is that the repack succeeds, but the netstandard.dll reference still needs to be resolved outside the EXE, which as far as I can tell would require installing mono-devel on Ubuntu, bloating the metadata tester container by ~300 MiB. This suggests to me that the copy of netstandard.dll that mono-devel installs is meant to be repacked, not referenced at runtime.

Presumably ILRepack would do this itself by default if it was a newer, more up to date tool, but this netstandard stuff is a bit newfangled for it, so we have to help it out.

Changes

• ILRepack is updated from 2.0.18 to 2.0.27 to get better netstandard support (ILRepack's developer just started making releases a month ago after almost 5 years!)
• The netstandard.library path is removed from ILRepack's Libs argument
• The path to the netstandard facade DLL is added to the assemblyPaths. This is a ~90 KiB file that just tells Mono to look up the references in .NET Framework since that's what the repacked EXE is built for.

In my testing, this allows the metadata tester to run.