Clear warnings about conflicting types

[ianleeder]

This resolves 4 compiler warnings.

Based off this comment, CS0436 looks like this:

\Source\Common\Util\Endpoints.cs(10,66): warning CS0436: The type NotNullWhenAttribute in \Source\Common\Util\CompilerTypes.cs conflicts with the imported type NotNullWhenAttribute in mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089. Using the type defined in \Source\Common\Util\CompilerTypes.cs.

Basically some newer features from .NET Core have been replicated in this codebase to support .NET Framework. In other languages we'd call this a polyfill.

It turns out to be harder to disable this in-code than expected, because the compiler warns on a generated file:

\Source\MultiplayerLoader\obj\Debug\MultiplayerLoader.AssemblyInfo.cs(13,44): warning CS0436: The type 'IgnoresAccessChecksToAttribute'...

//------------------------------------------------------------------------------
// <auto-generated>
//     This code was generated by a tool.
//
//     Changes to this file may cause incorrect behavior and will be lost if
//     the code is regenerated.
// </auto-generated>
//------------------------------------------------------------------------------

using System;
using System.Reflection;

// The class IgnoresAccessChecksToAttribute triggers this warning
[assembly: System.Runtime.CompilerServices.IgnoresAccessChecksToAttribute("0Harmony")]
[assembly: System.Runtime.CompilerServices.IgnoresAccessChecksToAttribute("Assembly-CSharp")]

And the generated file is... regenerated on each build. Changes do not persist.

So instead of suppressing on a case-by-case basis (which was already a flimsy solution), we can simply suppress this warning in .editorconfig.

There is also some serious irony that the file specifying that trailing whitespace should be eliminated contained trailing whitespace: