Automatically add label to Bottlerocket nodes for agent scheduling

**What I'd like:**

The update operator should automatically be eligible for scheduling on to Bottlerocket hosts in a Kubernetes cluster.

The suggested deployment uses a label to identify Bottlerocket hosts and schedule on them (ie: the `bottlerocket.aws/platform-version` label. Name may change: #4). Instead of requiring the label to be set by administrators, the label could be set (or determined) automatically for Bottlerocket nodes to eliminate the manual step.