Fix Windows CI: pin to windows-2022 (VS2022 generator missing on new image) (#1742)

## Problem

Every Windows/UWP job is failing at the configure step:

```
Image: windows-2025-vs2026
cmake -G "Visual Studio 17 2022" ...
CMake Error at CMakeLists.txt:16 (project):
  Generator
    Visual Studio 17 2022
  could not find any instance of Visual Studio.
```

GitHub repointed the `windows-latest` label to an image
(`windows-2025-vs2026`) that ships **only Visual Studio 2026, no
VS2022**. Our workflows configure with the hard-coded `Visual Studio 17
2022` CMake generator, so configuration fails before anything is built.
`master` looks green only because its checks are cached from before the
image change.

## Fix

Pin the four Windows workflows to the `windows-2022` runner, which still
provides the VS2022 toolset the generator targets:

- `build-win32.yml`
- `build-uwp.yml`
- `build-win32-shader.yml`
- `test-install-win32.yml`

This is the minimal, decoupled fix: it restores green CI immediately and
keeps the known-good toolchain. It also side-steps the unrelated MSVC
**C4875** GSL deprecation that the VS2026 toolset surfaces (handled
separately upstream in JsRuntimeHost).

Migrating to the VS2026 generator can be done later as a deliberate
follow-up once the toolchain churn settles.

Co-authored-by: Branimir Karadžić <branimirk@microsoft.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: 3 people

.github/workflows/build-uwp.yml

@@ -13,7 +13,7 @@ on:
 
 jobs:
   build:
-    runs-on: windows-latest
+    runs-on: windows-2022
     timeout-minutes: 30
     steps:
       - uses: actions/checkout@v5

.github/workflows/build-win32-shader.yml

@@ -10,7 +10,7 @@ on:
 
 jobs:
   build:
-    runs-on: windows-latest
+    runs-on: windows-2022
     timeout-minutes: 30
     steps:
       - uses: actions/checkout@v5

.github/workflows/build-win32.yml

@@ -21,7 +21,7 @@ on:
 
 jobs:
   build:
-    runs-on: windows-latest
+    runs-on: windows-2022
     timeout-minutes: 60
     steps:
       - uses: actions/checkout@v5

.github/workflows/test-install-win32.yml

@@ -5,7 +5,7 @@ on:
 
 jobs:
   test-install:
-    runs-on: windows-latest
+    runs-on: windows-2022
     timeout-minutes: 30
     steps:
       - uses: actions/checkout@v5

Apps/ModuleLoadTest/Source/App.Win32.cpp

@@ -129,6 +129,10 @@ namespace ModuleLoadTest
             "dxil.dll",
             // VS Start-Without-Debugging launch environment
             "kernel.appcore.dll",
+            // Ambient shell/appcore DLL pulled in transitively (e.g. via
+            // windows.storage.dll / DComp) on some Windows images such as the
+            // GitHub windows-2022 runner; not introduced by BabylonNative.
+            "twinapi.appcore.dll",
         };
         for (const auto& prefix : kPrefixes)
         {