Make upgrade install new host first, then uninstall old (#60325)

This should preserve the ordering of PATH, since the old MSI will never
remove its entry.

Author: ericstj

src/installer/pkg/projects/Microsoft.NETCore.DotNetHost/Microsoft.NETCore.DotNetHost.pkgproj

@@ -15,6 +15,7 @@
       <WixProductMoniker>$(SharedHostBrandName)</WixProductMoniker>
       <RegKeyProductName>sharedhost</RegKeyProductName>
       <WixDependencyKeyName>Dotnet_CLI_SharedHost</WixDependencyKeyName>
+      <MajorUpgradeSchedule>afterInstallExecute</MajorUpgradeSchedule>
       <VSInsertionShortComponentName>SharedHost</VSInsertionShortComponentName>
 
       <PublishRootDir>$(IntermediateOutputPath)publishRoot/</PublishRootDir>