Write a unit test to make sure `sliceState` is set to 0 between TAS fitting consecutive PodSets in a single Workload

[lchrzaszcz]

What would you like to be cleaned:
Slice-level topology in Kueue TAS has been added recently:

• Add PodSet Slice API #5596 - new API
• Two level TAS scheduling / PodSet chunk topology #5353 - TAS algorithm change
• Validate slice annotations #5582 - validation of the annotations

As suggested in a comment we should add unit test with two or more PodSets that check if we actually reset the sliceState between trying to fit consecutive PodSets from the same Workload.

It would be best to tackle this task first to add a new test in already consolidated suite.

Why is this needed:
As far as I know we had a hard to track bug connected with not resetting state, which is similar to sliceState. Given that, we should write a test for this as it is easy to break in the future.