Update the helm hook to apply the VMSS label instead of annotations.

[Mossaka]

re: #24

After runtime-class-manager supports node labels, the helm hook should apply the vmss label instead of annotations. Labels set at the VMSS level are automatically applied to all new nodes within a NodePool, ensuring that new nodes inherit the necessary labels even after reallocation.@vdice

[macolso]

Is node label support on the immediate roadmap for runtime-class-manager? Asking because we may want to take @ThorstenHans up on his offer in #24 to document his workaround in the meantime if there's going to be a wait.

[vdice]

Runtime-class-manager does operate on the level of labels today, so when kwasm-operator is replaced by it, we can indeed update the helm hook. However, the main prerequisite for swapping in rcm is currently distro support parity with kwasm-operator, with completing the node controller functionality a close second (though if in a time crunch, this could be argued as more of a feature that kwasm-operator doesn't support but we'd get with rcm)