Godot crashes when recompiling gdext and reloading scene while signal connected

Add the following node to scene and at this point scene reloading works fine. However, once you recompile gdext and then reload the scene, Godot will crash.
```rust
#[derive(GodotClass)]
#[class(base=Node3D,tool,init)]
struct MyNode3D {
base: Base,
}

#[godot_api]
impl INode3D for MyNode3D {
fn ready(&mut self) {
self.signals().visibility_changed().connect_self(|this| {
let is_visible = this.base().is_visible();
godot_print!("visibility: {}", is_visible);
});
}
```
Call stack:
```
7F178031BE90 (Unknown Source:0)
CallableCustomExtension::~CallableCustomExtension() (/home/luo/godot/core/extension/gdextension_interface.cpp:232)
void memdelete(CallableCustom*) (/home/luo/godot/core/os/memory.h:139)
Callable::~Callable() (/home/luo/godot/core/variant/callable.cpp:442)
KeyValue::~KeyValue() (/home/luo/godot/core/templates/pair.h:64)
HashMapElement::~HashMapElement() (/home/luo/godot/core/templates/hash_map.h:55)
void memdelete>(HashMapElement*) (/home/luo/godot/core/os/memory.h:139)
DefaultTypedAllocator>::delete_allocation(HashMapElement*) (/home/luo/godot/core/os/memory.h:258)
HashMap, HashMapComparatorDefault, DefaultTypedAllocator>>::clear() (/home/luo/godot/core/templates/hash_map.h:257)
HashMap, HashMapComparatorDefault, DefaultTypedAllocator>>::~HashMap() (/home/luo/godot/core/templates/hash_map.h:641)
Object::SignalData::~SignalData() (/home/luo/godot/core/object/object.h:613)
KeyValue::~KeyValue() (/home/luo/godot/core/templates/pair.h:64)
HashMapElement::~HashMapElement() (/home/luo/godot/core/templates/hash_map.h:55)
void memdelete>(HashMapElement*) (/home/luo/godot/core/os/memory.h:139)
DefaultTypedAllocator>::delete_allocation(HashMapElement*) (/home/luo/godot/core/os/memory.h:258)
HashMap, DefaultTypedAllocator>>::erase(StringName const&) (/home/luo/godot/core/templates/hash_map.h:356)
Object::~Object() (/home/luo/godot/core/object/object.cpp:2290)
Node::~Node() (/home/luo/godot/scene/main/node.cpp:4083)
Node3D::~Node3D() (/home/luo/godot/scene/3d/node_3d.cpp:1555)
void memdelete(Node*) (/home/luo/godot/core/os/memory.h:139)
```

Reproduce the crash with the provided Rust MyNode3D signal connection, then inspect the cleanup path starting at CallableCustomExtension::~CallableCustomExtension() in core/extension/gdextension_interface.cpp and the signal destruction frames listed in the call stack. Done means recompiling gdext and reloading the scene no longer crashes when the visibility_changed connection is cleaned up.

Written by the indexing model from the issue text.