AtlasEngine: Fix ClearType being always enabled (#12705)

HLSL uses 32-bit booleans, while C++ uses 8-bit ones aligned by 32-bit.
This meant that the shader was accessing uninitialized memory
forcing ClearType blending to be randomly enabled.

This regressed in commit 5964060.

## PR Checklist
* [x] I work here
* [x] Tests added/passed

## Validation Steps Performed
* ClearType blending works ✅
* Enabling transparent backgrounds forces grayscale blending ✅

src/renderer/atlas/AtlasEngine.h

@@ -555,6 +555,8 @@ namespace Microsoft::Console::Render
             // * Members cannot straddle 16 byte boundaries
             //   This means a structure like {u32; u32; u32; u32x2} would require
             //   padding so that it is {u32; u32; u32; <4 byte padding>; u32x2}.
+            // * bool will probably not work the way you want it to,
+            //   because HLSL uses 32-bit bools and C++ doesn't.
             alignas(sizeof(f32x4)) f32x4 viewport;
             alignas(sizeof(f32x4)) f32 gammaRatios[4]{};
             alignas(sizeof(f32)) f32 enhancedContrast = 0;
@@ -565,7 +567,7 @@ namespace Microsoft::Console::Render
             alignas(sizeof(u32)) u32 backgroundColor = 0;
             alignas(sizeof(u32)) u32 cursorColor = 0;
             alignas(sizeof(u32)) u32 selectionColor = 0;
-            alignas(sizeof(u32)) bool useClearType = 0;
+            alignas(sizeof(u32)) u32 useClearType = 0;
 #pragma warning(suppress : 4324) // 'ConstBuffer': structure was padded due to alignment specifier
         };
 

src/renderer/atlas/shader_ps.hlsl

@@ -48,7 +48,7 @@ cbuffer ConstBuffer : register(b0)
     uint backgroundColor;
     uint cursorColor;
     uint selectionColor;
-    bool useClearType;
+    uint useClearType;
 };
 StructuredBuffer<Cell> cells : register(t0);
 Texture2D<float4> glyphs : register(t1);