LibJS: Exclude FinalizationRegistries with queued cleanup jobs from GC

This is done by just adding them to the list of GC roots, which
prevents the VM from trying to run cleanup job of garbage collected
registries.

Userland/Libraries/LibJS/Runtime/VM.cpp

@@ -120,6 +120,9 @@ void VM::gather_roots(HashTable<Cell*>& roots)
 
     for (auto* job : m_promise_jobs)
         roots.set(job);
+
+    for (auto* finalization_registry : m_finalization_registry_cleanup_jobs)
+        roots.set(finalization_registry);
 }
 
 Symbol* VM::get_global_symbol(const String& description)