Cherry-pick upstream PR rwmt#800: normalize stack trace file paths

From rwmt#800 (commit 3ff1ab9):
- Use PathMap compiler option to shorten stack trace paths

Author: matthewwachter

Source/Client/Multiplayer.csproj

@@ -64,6 +64,10 @@
     <ModOutputPath>..\..\</ModOutputPath>
   </PropertyGroup>
 
+  <PropertyGroup Label="Normalise stack trace file locations">
+    <PathMap>$([System.IO.Path]::GetFullPath('$(MSBuildThisFileDirectory)'))=$(AssemblyName)/</PathMap>
+  </PropertyGroup>
+
   <Target Name="CopyToRimworld" AfterTargets="Build">
     <Copy SourceFiles="bin\Multiplayer.dll" DestinationFiles="$(ModOutputPath)\AssembliesCustom\Multiplayer.dll" />
     <Copy SourceFiles="bin\Multiplayer.pdb" DestinationFiles="$(ModOutputPath)\AssembliesCustom\Multiplayer.pdb" />

Source/Common/Common.csproj

@@ -27,4 +27,7 @@
     </PropertyGroup>
   </Target>
 
+  <PropertyGroup Label="Normalise stack trace file locations">
+    <PathMap>$([System.IO.Path]::GetFullPath('$(MSBuildThisFileDirectory)'))=$(AssemblyName)/</PathMap>
+  </PropertyGroup>
 </Project>

Source/MultiplayerLoader/MultiplayerLoader.csproj

@@ -31,4 +31,7 @@
     </PropertyGroup>
   </Target>
 
+  <PropertyGroup Label="Normalise stack trace file locations">
+    <PathMap>$([System.IO.Path]::GetFullPath('$(MSBuildThisFileDirectory)'))=$(AssemblyName)/</PathMap>
+  </PropertyGroup>
 </Project>