Migrate from Endpoints to EndpointSlice

[mflendrich]

Is there an existing issue for this?

• I have searched the existing issues

Problem Statement

KIC 2.x (at the moment of writing - 2.9) uses two different APIs for the same purpose:

• EndpointSlice for gateway discovery
• Endpoint for target generation

Proposed Solution

Drop Endpoint listeners in favor of discovery.k8s.io/v1 EndpointSlice.

Additional information

KIC 2.9's minimum supported k8s version is 1.22. 1.22 already includes EndpointSlice at v1, so this change should not be introducing new Kubernetes version breakage.

Acceptance Criteria

• getServiceEndpoints no longer relies on the Endpoint API (and uses EndpointSlice instead)
• KIC's usage of Endpoint Kubernetes resources is eradicated