`PackedVector3Array` function return type from `Array[Vector3i]` assigned to new `PackedVector3Array` variable results in reference

### Tested versions

Reproducible on Windows 10, v4.4.stable.official [4c311cbee]

### System information

Godot v4.4.stable - Windows 10 (build 19045) - Multi-window, 1 monitor - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 4070 (NVIDIA; 32.0.15.7260) - Intel(R) Core(TM) i7-6700K CPU @ 4.00GHz (8 threads)

### Issue description

### Findings
Checkout the working _GUT_ testing code:
```gdscript
func _testHelperWithWrongReturnType() -> PackedVector3Array:
var array: Array[Vector3i] = [Vector3i(1, 2, 3), Vector3i(4, 5, 6)]
return array

func test_PackedVector3ArrayFromArrayVector3iWrong():
var packedArray: PackedVector3Array = _testHelperWithWrongReturnType()
var secondArray: PackedVector3Array = packedArray
secondArray.clear()
assert_eq(packedArray, secondArray)

func test_PackedVector3ArrayFromArrayVector3iWrongTwo():
var packedArray: PackedVector3Array = PackedVector3Array(_testHelperWithWrongReturnType())
var secondArray: PackedVector3Array = packedArray
secondArray.clear()
assert_eq(packedArray, secondArray)

func test_PackedVector3ArrayFromArrayVector3iCorrectWithCopyConstructor():
var packedArray: PackedVector3Array = _testHelperWithWrongReturnType()
var secondArray: PackedVector3Array = PackedVector3Array(packedArray)
secondArray.clear()
assert_ne(packedArray, secondArray)

func test_PackedVector3ArrayFromArrayVector3iCorrectWithDuplicate():
var packedArray: PackedVector3Array = _testHelperWithWrongReturnType()
var secondArray: PackedVector3Array = packedArray.duplicate()
secondArray.clear()
assert_ne(packedArray, secondArray)
```
Be aware, that `PackedVector3Array` behaves at least strange when assigned from `Array[Vector3i]`:
* the cases with `assert_eq` are wrong in my eyes
* the cases with `assert_ne` are correct

### Expectation
Assigning variables of the type `PackedVector3Array` should be copied in any case as stated in the documentation.

### Steps to reproduce

see the GDScript example in the issue description

### Minimal reproduction project (MRP)

see the GDScript example in the issue description

Start with the GUT reproduction functions in the issue, especially the assignments from _testHelperWithWrongReturnType() and the copy-constructor comparison. Trace how PackedVector3Array handles these assignments, then add or update a regression test showing that assigned arrays are independent and that the existing copy constructor behavior remains correct.

Written by the indexing model from the issue text.