.NET10 Migration (#946)

Runtime and build
- Move all projects to .NET 10 with SDK-style project files and a shared
  Directory.Build.props (WIN/LINUX, x86/x64 defines)
- Load managed and unmanaged dependencies from libs/managed and
  libs/unmanaged through assembly and native library resolvers
- Compile party modes with Roslyn instead of CodeDom
- Update AppVeyor to the .NET 10 SDK and dotnet test
- Download the FFmpeg and gstreamer runtimes from the dependencies
  repository during the build
- Remove the VC++ 2015-2022 runtime check, no dependency needs it anymore

Graphics and windowing
- Replace the Direct3D 9 renderer with Direct3D 11 (Vortice)
- Pace Direct3D 11 frames with a frame latency waitable swap chain
- Move window, input and message boxes to SDL3
- Replace System.Drawing with SkiaSharp and WinForms with SDL3 and a
  software renderer

Video and audio
- Replace Acinerella with FFmpeg 8.1.3 (FFmpeg.AutoGen)
- Add hardware accelerated video decoding (D3D11VA, DXVA2, VideoToolbox,
  VAAPI, VDPAU) with software fallback
- Convert YUV video frames to RGB on the GPU in Direct3D 11 and OpenGL
- Add the video options HardwareDecoding, GpuColorConversion,
  DecoderThreads and VideoDownscaleResolution
- Update OpenAL to OpenTK 4 and NAudio recording to WasapiRecorder

Fixes
- Fix the song preview start and shorten the reporter buttons
- Fix a crash when opening the highscore without a selected song
- Use the options slide highlight in the party mode screens to avoid
  brightness flicker on VRR displays
- Disable GameInput in the x86 build, SDL3 crashes in GameInputCreate
  on 32-bit systems with the GameInput runtime installed
- Fix a truncation warning in PitchTracker

VocaluxeLib/CHelper.cs

@@ -22,6 +22,7 @@ using System.Globalization;
 using System.IO;
 using System.Linq;
 using System.Text.RegularExpressions;
+using SkiaSharp;
 using VocaluxeLib.Log;
 
 namespace VocaluxeLib
@@ -351,7 +352,7 @@ namespace VocaluxeLib
         /// </summary>
         /// <param name="filePath">Full path to image file</param>
         /// <returns>Bitmap or null on error</returns>
-        public static Bitmap LoadBitmap(string filePath)
+        public static SKBitmap LoadBitmap(string filePath)
         {
             if (!File.Exists(filePath))
             {
@@ -359,12 +360,17 @@ namespace VocaluxeLib
                 return null;
             }
 
-            Bitmap bmp;
+            SKBitmap bmp;
             try
             {
-                bmp = new Bitmap(filePath);
+                bmp = SKBitmap.Decode(filePath);
             }
             catch (Exception)
+            {
+                bmp = null;
+            }
+
+            if (bmp == null)
             {
                 CLog.Error("Error loading bitmap: " + filePath);
                 return null;