CmdPal: fix missing builtin icons (#41298)

It would seem that the way we absorb the icons for built-in extension
into our package relies on the _extension_ package including WASDK. I
don't fully understand why.

This PR adds a common `.props` file we can use for all extensions, to
make sure they include it.

regressed in #41261
Closes #41279

src/modules/cmdpal/ext/Microsoft.CmdPal.Ext.Shell/Microsoft.CmdPal.Ext.Shell.csproj

@@ -2,6 +2,8 @@
   <Import Project="..\..\..\..\Common.Dotnet.CsWinRT.props" />
   <Import Project="..\..\..\..\Common.Dotnet.AotCompatibility.props" />
 
+    <Import Project="..\Common.ExtDependencies.props" />
+
   <PropertyGroup>
 	<Nullable>enable</Nullable>
     <RootNamespace>Microsoft.CmdPal.Ext.Shell</RootNamespace>