Rename the PodMetrics type

[ahg-g]

Perhaps we can name it Endpoint

[kfswain]

I like ModelServerPod and then Metrics as a field of the struct. But I feel more strongly that we move away from PodMetrics than I do towards a specific name (so long as that name is an improvement.)

Let the Great Name Wars commence! 😆

[ahg-g]

Nit: in a multi-node setup, the server is not just a pod, it is a group of pods. While we could say that we only care about the single pod representing the group (aka the leader), an endpoint might be more generic here especially if we name the extension "Endpoint Picker".

[hzxuzhonghu]

The InferencePoolSpec.Selector documented to select model server pods, so how about ModelServerStats

[ahg-g]

ModelServer alone is another one?

I generally think this item is lower priority compared to increasing test coverage though.