Upgrade .NET Core 3.1 to .NET 5 (#15591)

* Common.UI

* ColorPicker

* PT Run

* File Explorer Add-ons

* Awake

* FZ Editor

* ImageResizer

* Interop

* Docs

* Installer

* Fix test not being run - Downgrade MSTest.TestAdapter & MSTest.TestFramework

* Update expect.txt

* Test run fix

src/modules/previewpane/GcodePreviewHandler/GcodePreviewHandler.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk.WindowsDesktop">
+<Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <Platforms>x64</Platforms>
     <UseWindowsForms>true</UseWindowsForms>
@@ -24,7 +24,7 @@
   <PropertyGroup>
     <ProjectGuid>{805306FF-A562-4415-8DEF-E493BDC45918}</ProjectGuid>
     <RootNamespace>Microsoft.PowerToys.PreviewHandler.Gcode</RootNamespace>
-    <TargetFramework>netcoreapp3.1</TargetFramework>
+    <TargetFramework>net5.0-windows10.0.18362.0</TargetFramework>
     <EnableComHosting>true</EnableComHosting>
     <IntermediateOutputPath>$(SolutionDir)$(Platform)\$(Configuration)\obj\$(AssemblyName)\</IntermediateOutputPath>
   </PropertyGroup>
@@ -63,13 +63,6 @@
     <ProjectReference Include="..\common\PreviewHandlerCommon.csproj" />
   </ItemGroup>
    
-  <ItemGroup>
-    <Reference Include="Windows">
-      <HintPath>$(MSBuildProgramFiles32)\Windows Kits\10\UnionMetadata\10.0.18362.0\Windows.winmd</HintPath>
-      <IsWinMDFile>true</IsWinMDFile>
-    </Reference>
-  </ItemGroup>
-   
   <ItemGroup>
     <EmbeddedResource Update="Properties\Resource.resx">
       <Generator>ResXFileCodeGenerator</Generator>