[vs17.12] Bump VS and xcopy-msbuild version to 17.12.0 (#11155)

* Bump up VS version to 17.12

* Bump up xcopy-msbuild to 17.12.0

* Bump up version prefix to 17.12.21

---------

Co-authored-by: Gang Wang <v-gaw@microsoft.com>

eng/Versions.props

@@ -2,7 +2,7 @@
 <!-- Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the MIT license. See License.txt in the project root for full license information. -->
 <Project>
   <PropertyGroup>
-    <VersionPrefix>17.12.20</VersionPrefix><DotNetFinalVersionKind>release</DotNetFinalVersionKind>
+    <VersionPrefix>17.12.21</VersionPrefix><DotNetFinalVersionKind>release</DotNetFinalVersionKind>
     <PackageValidationBaselineVersion>17.11.4</PackageValidationBaselineVersion>
     <AssemblyVersion>15.1.0.0</AssemblyVersion>
     <PreReleaseVersionLabel>preview</PreReleaseVersionLabel>

global.json

@@ -5,9 +5,9 @@
   "tools": {
     "dotnet": "9.0.100",
     "vs": {
-      "version": "17.10.0"
+      "version": "17.12.0"
     },
-    "xcopy-msbuild": "17.10.0-pre.4.0"
+    "xcopy-msbuild": "17.12.0"
   },
   "msbuild-sdks": {
     "Microsoft.DotNet.Arcade.Sdk": "9.0.0-beta.24572.2"