[K/N] Convert :kotlin-native:Interop:StubGenerator

Use folder structure from the rest of the project and build it by
the bootstrap compiler.

kotlin-native/Interop/StubGenerator/testResources/ForwardDeclarations/structWithDefinition/included.h

@@ -0,0 +1,3 @@
+struct Struct3;
+
+struct Struct4 {};

kotlin-native/Interop/StubGenerator/testResources/ForwardDeclarations/structWithDefinition/main.def

@@ -0,0 +1 @@
+headers = main.h

kotlin-native/Interop/StubGenerator/testResources/ForwardDeclarations/structWithDefinition/main.h

@@ -0,0 +1,12 @@
+#include "included.h"
+
+struct Struct1;
+struct Struct1 {};
+
+struct Struct2;
+struct Struct2 {};
+struct Struct2;
+
+struct Struct3 {};
+
+struct Struct4;