bpo-35976: Enable Windows projects to build with platform ARM32 (GH-11825)

This change adds the necessary items to the build projects to avoid erroring out right at the start. It does not add _support_ for targeting Windows on ARM32, but is a necessary prerequisite for adding it.
diff --git a/PCbuild/pythoncore.vcxproj b/PCbuild/pythoncore.vcxproj
index f33cdb5..b1b9944 100644
--- a/PCbuild/pythoncore.vcxproj
+++ b/PCbuild/pythoncore.vcxproj
@@ -1,6 +1,10 @@
 <?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|Win32">
       <Configuration>Debug</Configuration>
       <Platform>Win32</Platform>
@@ -9,6 +13,10 @@
       <Configuration>Debug</Configuration>
       <Platform>x64</Platform>
     </ProjectConfiguration>
+    <ProjectConfiguration Include="PGInstrument|ARM">
+      <Configuration>PGInstrument</Configuration>
+      <Platform>ARM</Platform>
+    </ProjectConfiguration>
     <ProjectConfiguration Include="PGInstrument|Win32">
       <Configuration>PGInstrument</Configuration>
       <Platform>Win32</Platform>
@@ -17,6 +25,10 @@
       <Configuration>PGInstrument</Configuration>
       <Platform>x64</Platform>
     </ProjectConfiguration>
+    <ProjectConfiguration Include="PGUpdate|ARM">
+      <Configuration>PGUpdate</Configuration>
+      <Platform>ARM</Platform>
+    </ProjectConfiguration>
     <ProjectConfiguration Include="PGUpdate|Win32">
       <Configuration>PGUpdate</Configuration>
       <Platform>Win32</Platform>
@@ -25,6 +37,10 @@
       <Configuration>PGUpdate</Configuration>
       <Platform>x64</Platform>
     </ProjectConfiguration>
+    <ProjectConfiguration Include="Release|ARM">
+      <Configuration>Release</Configuration>
+      <Platform>ARM</Platform>
+    </ProjectConfiguration>
     <ProjectConfiguration Include="Release|Win32">
       <Configuration>Release</Configuration>
       <Platform>Win32</Platform>