[vs-workload] Set EnableSideBySideManifests=true (#8179)

Context: xamarin/yaml-templates#274

Enables side by side workload manifest support when generating workload MSIs.

This should only be enabled for builds shipping with .NET 8 Preview 7 or later.

build-tools/create-packs/vs-workload.in.props

@@ -3,6 +3,7 @@
   <PropertyGroup>
     <TargetName>Microsoft.NET.Sdk.Android.Workload.@VSMAN_VERSION@</TargetName>
     <ManifestBuildVersion>@WORKLOAD_VERSION@</ManifestBuildVersion>
+    <EnableSideBySideManifests>true</EnableSideBySideManifests>
   </PropertyGroup>
   <ItemGroup>
     <!-- Shorten package names to avoid long path caching issues in Visual Studio -->