bpo-33125: Add support for building and releasing Windows ARM64 packages (GH-16828)

Note that the support is not actually enabled yet, and so we won't be publishing these packages. However, for those who want to build it themselves (even by reusing the Azure Pipelines definition), it's now relatively easy to enable.
diff --git a/PCbuild/pythonw_uwp.vcxproj b/PCbuild/pythonw_uwp.vcxproj
index e2c0171..828d0d1 100644
--- a/PCbuild/pythonw_uwp.vcxproj
+++ b/PCbuild/pythonw_uwp.vcxproj
@@ -1,6 +1,14 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Project DefaultTargets="Build" ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <ItemGroup Label="ProjectConfigurations">
+    <ProjectConfiguration Include="Debug|ARM">
+      <Configuration>Debug</Configuration>
+      <Platform>ARM</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Debug|ARM64">
+      <Configuration>Debug</Configuration>
+      <Platform>ARM64</Platform>
+    </ProjectConfiguration>
     <ProjectConfiguration Include="Debug|Win32">
       <Configuration>Debug</Configuration>
       <Platform>Win32</Platform>
@@ -9,6 +17,14 @@
       <Configuration>Debug</Configuration>
       <Platform>x64</Platform>
     </ProjectConfiguration>
+    <ProjectConfiguration Include="PGInstrument|ARM">
+      <Configuration>PGInstrument</Configuration>
+      <Platform>ARM</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="PGInstrument|ARM64">
+      <Configuration>PGInstrument</Configuration>
+      <Platform>ARM64</Platform>
+    </ProjectConfiguration>
     <ProjectConfiguration Include="PGInstrument|Win32">
       <Configuration>PGInstrument</Configuration>
       <Platform>Win32</Platform>
@@ -17,6 +33,14 @@
       <Configuration>PGInstrument</Configuration>
       <Platform>x64</Platform>
     </ProjectConfiguration>
+    <ProjectConfiguration Include="PGUpdate|ARM">
+      <Configuration>PGUpdate</Configuration>
+      <Platform>ARM</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="PGUpdate|ARM64">
+      <Configuration>PGUpdate</Configuration>
+      <Platform>ARM64</Platform>
+    </ProjectConfiguration>
     <ProjectConfiguration Include="PGUpdate|Win32">
       <Configuration>PGUpdate</Configuration>
       <Platform>Win32</Platform>
@@ -25,6 +49,14 @@
       <Configuration>PGUpdate</Configuration>
       <Platform>x64</Platform>
     </ProjectConfiguration>
+    <ProjectConfiguration Include="Release|ARM">
+      <Configuration>Release</Configuration>
+      <Platform>ARM</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Release|ARM64">
+      <Configuration>Release</Configuration>
+      <Platform>ARM64</Platform>
+    </ProjectConfiguration>
     <ProjectConfiguration Include="Release|Win32">
       <Configuration>Release</Configuration>
       <Platform>Win32</Platform>