feat: allow to configure livekit Deployment as StatefulSet

[holzgeist]

This change allows Livekit to be deployed as a StatefulSet instead of a Deployment.

Motivation

Our main setup are 3 nodes on a fixed pool. For scaling we use a different, dynamic pool and when scaling down, we of course want pods from the dynamic pool to be selected for killing. Otherwise, when scaling down the pool we will have to move a pod again. Apparently Kubernetes doesn't expose many options to select pods for scaling down, so we came up with this approach.

For a StatefulSet with scale N, Kubernetes guarantees to kill pod N-1 when scaling down. As our base nodes will always have indices 0-2, this approach will guarantee killing a pod on the dynamic pool

TBD

The current change lets the user define the deployment kind as a raw field, where really only two values are supported. One other way I can think of would be a boolean deployAsStatefulSet variable that then selects the proper value in the templates.

[holzgeist]

Update: We will go with a single scaling pool after all, closing this PR