feat: skip init for value type

Author: Vyacheslav

Src/StackMemoryCollections/GenerateStack.cs

@@ -675,7 +675,7 @@ private void StackTop(
             in string sizeOfStr
             )
         {
-            if (typeInfo.IsUnmanagedType)
+            if (typeInfo.IsValueType)
             {
                 builder.Append($@"
         [SkipLocalsInit]

Src/Tests/StackOfTestStructFixture.cs

@@ -1,8 +1,5 @@
 using NUnit.Framework;
-using StackMemoryAttributes.Attributes;
-using StackMemoryCollections.Attibutes;
 using System;
-using System.Collections.Generic;
 using System.Runtime.CompilerServices;
 
 namespace Tests