Upgrade VSharp.Runner to net8

Author: cat923

VSharp.Runner/VSharp.Runner.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
-        <TargetFramework>net7.0</TargetFramework>
+        <TargetFramework>net8.0</TargetFramework>
         <OutputType>Exe</OutputType>
         <RootNamespace>VSharp.Runner</RootNamespace>
         <Configurations>Debug;Release;DebugTailRec</Configurations>