LibELF: Check if initializers ran instead of trusting s_global_objects

The original heuristic of "a library being in `s_global_objects` means
that it was fully initialized already" doesn't hold up anymore since we
changed the loading order. This was causing us to skip parts of the
initialization of dependency libraries when running dlopen (since it was
the only user of that setting).

Instead, set a flag after we run stage 4 (which is the "run the global
initializers" stage) and check that flag when determining unfinished
dependencies. This entirely replaces the `skip_global_objects` logic.

Userland/Libraries/LibELF/DynamicLoader.cpp

@@ -249,6 +249,8 @@ Result<NonnullRefPtr<DynamicObject>, DlErrorMessage> DynamicLoader::load_stage_3
 void DynamicLoader::load_stage_4()
 {
     call_object_init_functions();
+
+    m_fully_initialized = true;
 }
 
 void DynamicLoader::do_lazy_relocations()