`IsInstanceValid` called before the end of the frame returns true on an object that called `QueueFree`

### Tested versions

tested on v4.3.stable.mono.official

### System information

Windows 10 - Godot v4.3.stable.mono.official

### Issue description

If we call `node.QueueFree()`, `IsInstanceValid(node)` should return `false` even before the end of the frame.
I can't think of a reason why would anyone need to have `IsInstanceValid(node)` returning true after a `node.QueueFree()` call.

### Steps to reproduce

1. Create a node,
2. Print out `IsInstanceValid`
3. QueueFree the node
4. Print out `IsInstanceValid`

It prints out
```
true
true
```

and I think it must print out

```
true
false
```

### Minimal reproduction project (MRP)

```
ColorRect n = new ColorRect();
AddChild(n);
GD.Print(IsInstanceValid(n));
n.QueueFree();
GD.Print(IsInstanceValid(n));
```

Start with the minimal reproduction shown in the issue and run it against Godot v4.3.stable.mono.official to confirm the lifecycle behavior around QueueFree and IsInstanceValid. Trace the engine's object-deletion and validity checks, then verify that the documented expected output is produced without breaking queued deletion semantics.

Written by the indexing model from the issue text.