NGF: Update control data plane split telemetry

[bjee19]

Proposed changes

Update docs for CP/DP split telemetry changes.

Problem: Some small docs changes are needed for the new telemetry metrics/changes introduced with the control data plane split.

Solution: Add the new metrics. Also updated the data plane configuration document small error of including the namespace field in the gateway.infrastructure.parametersRef field since that does not exist: https://gateway-api.sigs.k8s.io/reference/spec/#localparametersreference.

Note: Left out GatewayAttachedNginxProxies in the document since I think it falls under the "we collect a count of NginxProxies"

Testing:

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