Detect conflicting version assignment rule updates

[jlegrone]

It is possible for multiple Temporal clients to make updates to assignment rules that conflict with each other. Eg.

• Two workers deployed in different k8s namespaces or k8s clusters
• A human operator manually editing assignment rules via the temporal CLI
• Any other client that manages assignment rules

The controller should set ownership metadata on each assignment rule that it creates, and switch to manual mode when it observes an active assignment rule that is not managed by itself.

Switching out of manual mode might require another API call to Temporal (eg. to update the ownership metadata).