atelet: change default port from 8085 to 24924

[Steven Linde (linde)]

Changes atelet's default gRPC port (atelet.DefaultPort, also its hostPort) from 8085 to 24924, so it is less likely to conflict with other processes on the node. atelet is the only Substrate component with a node-IP port.

By "node-IP port" we mean any port that accepts connections on the node's own IP, i.e. in the host network namespace, whether via hostPort, hostNetwork, or a NodePort Service. These share one port space with kubelet, other DaemonSets, and anything else on the VM. Pod-network ports live in each pod's own namespace and can't collide.

Notes for reviewers:

• Only node-IP ports are in scope. Pod-network listeners keep their defaults. That includes atunnel's ingress, CONNECT and egress ports on worker pods (443/8443/15001; the router dials workerIP:443 directly), the router, the credential providers, and metrics/health.
• ateapi dials atelet.DefaultPort, so ateapi and atelet need to roll out together.
• If Substrate needs more node-IP ports later, we recommend 24928, 24930 and 24934, in that order. Like 24924, they are not assigned by IANA and are rarely used.