Fix centrally-versioned package references (#4674)

* Use CentralPackageVersions in VSIX projects

* Turns out we just need to make sure to import the Directory.Build.props at the root

* Revert "Use CentralPackageVersions in VSIX projects"

This reverts commit 3446e0c.

* Don't include the entire root Directory.build.props

Directory.Packages.props

@@ -2,10 +2,7 @@
     This is the project file used by CentralPackageVersions, and used to control all PackageReference's
     and make sure the version is only declared in a single place
 
-    In order to the CentralPackageVersions, add this to your SDK-Style .csproj file:
-    <Sdk Name="Microsoft.Build.CentralPackageVersions" Version="2.0.1" />
-
-    For more info: https://github.com/microsoft/MSBuildSdks/tree/master/src/CentralPackageVersions
+    https://learn.microsoft.com/en-us/nuget/consume-packages/Central-Package-Management
 -->
 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <ItemGroup>

dev/VSIX/Directory.Build.props

@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+    <!-- NOTE: This file does not import Directory.Build.props in parent dirs -->
 
     <!-- Provide default nuget feed (Windows App SDK internal) and package versions for developer builds -->
     <PropertyGroup>
@@ -11,6 +12,8 @@
         <Deployment Condition="'$(Deployment)' == '' ">Standalone</Deployment>
         <!-- Don't automatically deploy the extension to the test VS environment during the build -->
         <DeployExtension>false</DeployExtension>
+
+        <ManagePackageVersionsCentrally>true</ManagePackageVersionsCentrally>
     </PropertyGroup>
 
     <!-- Useful folder paths -->
@@ -38,5 +41,4 @@
         <OutputPath>$(IntermediateOutputPath)</OutputPath>
         <OutDir>$(OutputPath)</OutDir>
     </PropertyGroup>
-
 </Project>