Test more cases of upgrade of workload cluster

A sylva version is support 3 versions of K8S for the workload cluster. Let's call them version N, N-1, N-2

Workload cluster operation support upgrades from N-2 to N-1 and from N-1 to N.

Today in CI we're only testing the case N-1 to N.

We now need to extend our CI coverage to cover more cases as we now have real deployment using N-2 version for example after an upgrade from sylva 1.4 to sylva 1.6 => here after this upgrade workload cluster will be running K8S 1.31 and we need to maje sure that they can be upgraded up to 1.33

We need to decide if :

• we treat the two steps independantly (ie a pipeline testing N-2 to N-1 and another testing N-1 to N)
• we want a single pipeline testing N-2 to N-1 to N

cc @loic.nicolle @matrohon @tmmorin @feleouet @sakuchoudhary98