Add unit tests for `ReflectionProbe`

[Gurka2]

Added tests for the class Reflection Probe

The tests test the class getters and setters and the function get aabb. This is what was asked in the issue https://github.com/godotengine/godot/issues/43440.

[dustdfg]

There is one problem. You used merge commit instead of rebasing

[AThousandShips]

When this has been reviewed it will need to be squashed, but please use rebase in the future instead, see here

[Gurka2]

I will fix the commit history some time next week :+1: :slightly_smiling_face:

[Gurka2]

@dustdfg @AThousandShips I think i fixed the git merge now :slightly_smiling_face: I configured the git config to rebase aswell