Add a dedicated listener port for envoy proxy readiness

[arkodg]

Description:

Describe the issue.

Currently the envoy proxy readiness port is 19001 and is shared with prometheus. This has two issues

• there's no clean way to change the prometheus port w/o affecting the readiness port follow up: make port 19001 configurable #1703
• the readiness port cannot be separated from the prometheus port and be converted into a dynamic xds listener to add more accuracy into the pod readiness Improve EG Gateway xDS & startup Reliability (custom k8s health prob) #2810 (comment)

If this proposal is accepted, a another port 19002 would be added and dedicated for readiness

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Any extra documentation required to understand the issue.

[arkodg]

ptal @envoyproxy/gateway-maintainers @envoyproxy/gateway-reviewers

[shawnh2]

+1, 19001 should be readiness port, 19002 can be used for prometheus

[arkodg]

@shawnh2 moving prom to 19002 will be a breaking change for existing users, so prefer keeping prom on 19001, and readiness on 19002, readiness port is used internally ideally only by kubelet so it shouldnt affect users

[shawnh2]

@shawnh2 moving prom to 19002 will be a breaking change for existing users, so prefer keeping prom on 19001, and readiness on 19002, readiness port is used internally ideally only by kubelet so it shouldnt affect users

SGTM