Update SplashScreen to use CsWin32 and shared library

This updates SplashScreen to use direct interop built on CsWin32. It also uses the shared `System.Private.Windows.Core` library built in Windows Forms.

This makes SplashScreen trim-friendly and improves the performance as it will no longer need to generate the rather extensive interop it used to at startup.

This also introduces a bottom level assembly for WPF: `System.Windows.Primitives` where there are no other dependencies other than the WinForms/WPF base assembly: `System.Private.Windows.Core`.

`PInvokeCore` is the static class that comes from `System.Private.Windows.Core`. `PInvoke` is the static class from `System.Windows.Primitives`. When C# adds something akin to extension types (currently in the design phase) we'll be able to unify to a single `PInvoke`. Generated types (such as `HWND`) are in the namespaces as specified by the Windows metdata and don't have the same problem with conflicts as CsWin32 won't generate types that already exist.

CsWin32 uses `System.Drawing` types where they match Win32 types. `Point` is an example of this. These interchange `System.Drawing` types are in-box with .NET.

`System.Private.Windows.Core` provides a lot of useful support functionality, particularly when it comes to interop. The various scope types in this PR are an example. OLE code will come from this assembly after the new APIs are merged in WinForms.

I've also deleted a large swath of unused interop.

It leverages dotnet#10023, which leverages dotnet#9914 (the first commit), and will be updated when those are merged.

This is an update of dotnet#7929.

eng/Versions.props

@@ -81,6 +81,7 @@
     <!-- These versions are specified in global.json -->
     <StrawberryPerlVersion>5.38.0.1</StrawberryPerlVersion>
     <NetFramework48RefAssembliesVersion>0.0.0.1</NetFramework48RefAssembliesVersion>
+    <MicrosoftWindowsCsWin32PackageVersion>0.3.106</MicrosoftWindowsCsWin32PackageVersion>
   </PropertyGroup>
   <!-- External Analyzers -->
   <PropertyGroup>

eng/WpfArcadeSdk/tools/SdkReferences.targets

@@ -97,6 +97,16 @@
     </ItemGroup>
   </Target>
 
+  <Target Name="SplitTargetFramework">
+    <PropertyGroup>
+      <!-- Split out the target framework. "net10.0-windows" is an example. -->
+      <_targetFrameworkIdentifier>$([MSBuild]::GetTargetFrameworkIdentifier($(TargetFramework)))</_targetFrameworkIdentifier>
+      <_targetFrameworkIdentifier Condition="'$(_targetFrameworkIdentifier)' == '.NETCoreApp'">net</_targetFrameworkIdentifier>
+      <_targetFrameworkVersion>$([MSBuild]::GetTargetFrameworkVersion($(TargetFramework)))</_targetFrameworkVersion>
+      <_targetFrameworkRoot>$(_targetFrameworkIdentifier)$(_targetFrameworkVersion)</_targetFrameworkRoot>
+    </PropertyGroup>
+  </Target>
+
   <!--
     In your project, Add a references to WinForms transport package like this:
       <ItemGroup>
@@ -109,12 +119,13 @@
       </ItemGroup>
    -->
   <Target Name="ResolveWinFormsReferences"
+          DependsOnTargets="SplitTargetFramework"
           Condition="'@(MicrosoftPrivateWinFormsReference)'!=''
                  And '$(TargetFrameworkIdentifier)' == '.NETCoreApp'
                  And $([MSBuild]::VersionGreaterThanOrEquals('$(TargetFrameworkVersion)', '3.0')) ">
     <PropertyGroup>
       <!-- Use the current TargetFramework if not otherwise specified for WinForms private package -->
-      <_WinFormsTargetFrameworkVersion Condition="'$(_WinFormsTargetFrameworkVersion)' == ''">$(TargetFramework)</_WinFormsTargetFrameworkVersion>
+      <_WinFormsTargetFrameworkVersion Condition="'$(_WinFormsTargetFrameworkVersion)' == ''">$(_targetFrameworkRoot)</_WinFormsTargetFrameworkVersion>
     </PropertyGroup>
     <ItemGroup>
       <Reference Include="$(PkgMicrosoft_Private_Winforms)\lib\$(_WinFormsTargetFrameworkVersion)\%(MicrosoftPrivateWinFormsReference.Identity).dll"

eng/WpfArcadeSdk/tools/WpfProjectReference.targets

@@ -21,6 +21,7 @@
 
   </ItemGroup>
   <ItemGroup>
+    <WpfProjectPath Include="System.Windows.Primitives" ProjectPath="$(WpfSourceDir)System.Windows.Primitives\System.Windows.Primitives.csproj" />
     <WpfProjectPath Include="System.Xaml" ProjectPath="$(WpfSourceDir)System.Xaml\System.Xaml.csproj" />
     <WpfProjectPath Include="WindowsBase" ProjectPath="$(WpfSourceDir)WindowsBase\WindowsBase.csproj" />
     <WpfProjectPath Include="DirectWriteForwarder" ProjectPath="$(WpfSourceDir)DirectWriteForwarder\DirectWriteForwarder.vcxproj">