.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

Directory.Build.props

@@ -0,0 +1,57 @@
+<Project>
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <Configurations>DebugWin;ReleaseWin;InstallerWin;DebugLinux;ReleaseLinux</Configurations>
+    <Platforms>AnyCPU;x86;x64</Platforms>
+    <AppendTargetFrameworkToOutputPath>false</AppendTargetFrameworkToOutputPath>
+    <AppendRuntimeIdentifierToOutputPath>false</AppendRuntimeIdentifierToOutputPath>
+    <SatelliteResourceLanguages>en</SatelliteResourceLanguages>
+    <Prefer32Bit>false</Prefer32Bit>
+    <ErrorReport>prompt</ErrorReport>
+    <WarningLevel>4</WarningLevel>
+    <DebugType>portable</DebugType>
+    <DebugSymbols>true</DebugSymbols>
+    <CodeAnalysisRuleSet>$(MSBuildThisFileDirectory)CheckingRules.ruleset</CodeAnalysisRuleSet>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="Exists('$(MSBuildProjectDirectory)\Properties\AssemblyInfo.cs')">
+    <GenerateAssemblyCompanyAttribute>false</GenerateAssemblyCompanyAttribute>
+    <GenerateAssemblyConfigurationAttribute>false</GenerateAssemblyConfigurationAttribute>
+    <GenerateAssemblyCopyrightAttribute>false</GenerateAssemblyCopyrightAttribute>
+    <GenerateAssemblyDescriptionAttribute>false</GenerateAssemblyDescriptionAttribute>
+    <GenerateAssemblyFileVersionAttribute>false</GenerateAssemblyFileVersionAttribute>
+    <GenerateAssemblyInformationalVersionAttribute>false</GenerateAssemblyInformationalVersionAttribute>
+    <GenerateAssemblyProductAttribute>false</GenerateAssemblyProductAttribute>
+    <GenerateAssemblyTitleAttribute>false</GenerateAssemblyTitleAttribute>
+    <GenerateAssemblyVersionAttribute>false</GenerateAssemblyVersionAttribute>
+    <GenerateNeutralResourcesLanguageAttribute>false</GenerateNeutralResourcesLanguageAttribute>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="$(Configuration.StartsWith('Debug'))">
+    <Optimize>false</Optimize>
+    <DefineConstants>$(DefineConstants);TRACE;DEBUG</DefineConstants>
+  </PropertyGroup>
+  <PropertyGroup Condition="!$(Configuration.StartsWith('Debug'))">
+    <Optimize>true</Optimize>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="$(Configuration.EndsWith('Win'))">
+    <DefineConstants>$(DefineConstants);WIN</DefineConstants>
+    <NoWarn>$(NoWarn);CA1416</NoWarn>
+  </PropertyGroup>
+  <PropertyGroup Condition="$(Configuration.EndsWith('Linux'))">
+    <DefineConstants>$(DefineConstants);LINUX</DefineConstants>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)' == 'InstallerWin'">
+    <DefineConstants>$(DefineConstants);INSTALLER</DefineConstants>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="'$(Platform)' == 'x86'">
+    <PlatformTarget>x86</PlatformTarget>
+    <DefineConstants>$(DefineConstants);ARCH_X86</DefineConstants>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Platform)' == 'x64'">
+    <PlatformTarget>x64</PlatformTarget>
+    <DefineConstants>$(DefineConstants);ARCH_X64</DefineConstants>
+  </PropertyGroup>
+</Project>