[FFI][REFACTOR] Phase out getattr based attribute handling (apache#18189)

[REFACTOR] Phase out getattr based attribute handling

This PR phases out getattar based attribute handling as they are slower
and introduces extra code path.

This does mean that if an Object is not explicitly registered
in python side, we will no longer be able to access the field by name.
Likely this is also desirable as we would like to enable faster use that
updates the python end and do not rely on these behavior.

Author: tqchen

src/ffi/extra/serialization.cc

@@ -408,9 +408,20 @@ class ObjectGraphDeserializer {
 
 Any FromJSONGraph(const json::Value& value) { return ObjectGraphDeserializer::Deserialize(value); }
 
+// string version of the api
+Any FromJSONGraphString(const String& value) { return FromJSONGraph(json::Parse(value)); }
+
+String ToJSONGraphString(const Any& value, const Any& metadata) {
+  return json::Stringify(ToJSONGraph(value, metadata));
+}
+
 TVM_FFI_STATIC_INIT_BLOCK({
   namespace refl = tvm::ffi::reflection;
-  refl::GlobalDef().def("ffi.ToJSONGraph", ToJSONGraph).def("ffi.FromJSONGraph", FromJSONGraph);
+  refl::GlobalDef()
+      .def("ffi.ToJSONGraph", ToJSONGraph)
+      .def("ffi.ToJSONGraphString", ToJSONGraphString)
+      .def("ffi.FromJSONGraph", FromJSONGraph)
+      .def("ffi.FromJSONGraphString", FromJSONGraphString);
   refl::EnsureTypeAttrColumn("__data_to_json__");
   refl::EnsureTypeAttrColumn("__data_from_json__");
 });