[.Net / GDScript Interop] Cannot Call GDScript-Lambda-Backed `Callable` in C#

### Tested versions

v4.3.stable.mono.official [77dcf97d8]

### System information

Godot v4.3.stable.mono - Windows 10.0.17763 - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 4060 Ti (NVIDIA; 32.0.15.6109) - AMD Ryzen 9 5900X 12-Core Processor (24 Threads)

### Issue description

This is a niche use case, but we should document it if it's not supported.

In C# script, when trying to `Call()` a `Callable` that is backed by a `GDScript` `Lambda Expression`, Godot will produce the following error instead of actually making the call.

```
E 0:00:00:0894 main.gd:4 @ _ready(): Attempt to call callable 'null::null' on a null instance.
/root/godot/modules/mono/glue/GodotSharp/GodotSharp/Core/NativeInterop/ExceptionUtils.cs:160 @ void Godot.NativeInterop.ExceptionUtils.DebugCheckCallError(Godot.NativeInterop.godot_callable&, Godot.NativeInterop.godot_variant**, int, Godot.NativeInterop.godot_variant_call_error)
main.gd:4 @ _ready()
```

### Steps to reproduce

1. Create a C# Godot Project.
2. Create `main.gd`.
3. Create a scene, attach the `main.gd` to the root node, and save it to a file.
4. Create `Helper.cs`.
5. Run the project.

### Minimal reproduction project (MRP)

**main.gd**

```gdscript
extends Node

func _ready():
Helper.new().CallCallable(func(): print("Hello World"));
```

**Helper.cs**

```csharp
using Godot;

[GlobalClass]
public partial class Helper : Node
{
public void CallCallable(Callable callable) => callable.Call();
}
```

Reproduce the interop failure using main.gd and Helper.cs, especially Helper.CallCallable and the GDScript lambda passed to it. Read the reported call-error handling in modules/mono/glue/GodotSharp/GodotSharp/Core/NativeInterop/ExceptionUtils.cs. Done means determining whether this Callable combination should work and documenting the supported behavior or confirming the limitation.

Written by the indexing model from the issue text.