Generate structs for structs and fix struct out parameter if known (#8)

* Generate structs for structs and fix struct out parameter if known

* fmt

tests/ProxyInterfaceSourceGeneratorTests/Source/MyStruct.cs

@@ -1,6 +1,17 @@
 namespace ProxyInterfaceSourceGeneratorTests.Source;
 
 public struct MyStruct
+{
+    public int Id { get; set; }
+
+    public bool TryGetMyStruct2(int i, out MyStruct2 x, double z)
+    {
+        x = default;
+        return true;
+    }
+}
+
+public struct MyStruct2
 {
     public int Id { get; set; }
 }