Remove EndpointSlice dependency

[ahg-g]

The InferencePool API specs a pod selector for the endpoints, but the EPP implementation ignores that and uses a flag to a service ref.

Now that we landed on the pod selector approach after the API review, we need to switch to use the selector. This means:

• Removing the EndpointSlice reconciler
• Use InferencePool.Selector to list the pods and populate the datastore on every probe.

[danehans]

Dupe of #158

[danehans]

xref #252 to provide flexibility in InferencePool assignment.

[ahg-g]

Dupe of #158

This is more about removing the reconciler not just the flag.

[ahg-g]

/assign @kfswain

[ahg-g]

/reopen

[k8s-ci-robot]

@ahg-g: Reopened this issue.

In response to this:

/reopen

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