[4.4] Need update create_instance_func because godot gdextension_interface.h upgrade

[pupil1337]

Godot version

godot master branch

godot-cpp version

godot-cpp master branch

System information

windows 10, msvc, i7-9700

Issue description

Use deprecated=no build godot will has this problem, because gdextension_classdb_construct_object be marked deprecated.
Please update the new function.
(I didn't submit a PR because this upgrade maybe need modify memnew's postinitialize i can`t handle it.)

Steps to reproduce

1. Build godot custom args use deprecated=no. (godot: scons target=editor dev_build=yes... deprecated=no)
2. compile godot-cpp will successed.
3. open godot editor will error because cant find gdextension_classdb_construct_object.

Minimal reproduction project

N/A

[dsnopek]

Yep, it's on my TODO list!

Use deprecated=no build godot will has this problem, because gdextension_classdb_construct_object be marked deprecated.

If you're keeping up with Godot master and using deprecated=no, I suspect you will encounter this problem a few more times before Godot 4.4 is released. We can't always synchronize godot-cpp updates with Godot updates, even when we have a PR prepared in advance.

[pupil1337]

Yes, I switched to version 4.3 and everything is perfect!