NGF: Update control data plane split telemetry (#485)

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.

Author: bjee19

content/ngf/how-to/data-plane-configuration.md

@@ -260,7 +260,6 @@ infrastructure:
         group: gateway.nginx.org
         kind: NginxProxy
         name: ngf-proxy-config
-        namespace: default
 ```
 
 After updating, you can check the status of the Gateway to see if the configuration is valid:

content/ngf/overview/product-telemetry.md

@@ -28,11 +28,12 @@ Telemetry data is collected once every 24 hours and sent to a service managed by
 - **Cluster Node Count:** the number of Nodes in the cluster.
 - **Version:** the version of the NGINX Gateway Fabric Deployment.
 - **Deployment UID:** the UID of the NGINX Gateway Fabric Deployment.
-- **Deployment Replica Count:** the count of NGINX Gateway Fabric Pods.
 - **Image Build Source:** whether the image was built by GitHub or locally (values are `gha`, `local`, or `unknown`). The source repository of the images is **not** collected.
 - **Deployment Flags:** a list of NGINX Gateway Fabric Deployment flags that are specified by a user. The actual values of non-boolean flags are **not** collected; we only record that they are either `true` or `false` for boolean flags and `default` or `user-defined` for the rest.
 - **Count of Resources:** the total count of resources related to NGINX Gateway Fabric. This includes `GatewayClasses`, `Gateways`, `HTTPRoutes`,`GRPCRoutes`, `TLSRoutes`, `Secrets`, `Services`, `BackendTLSPolicies`, `ClientSettingsPolicies`, `NginxProxies`, `ObservabilityPolicies`, `UpstreamSettingsPolicies`, `SnippetsFilters`, and `Endpoints`. The data within these resources is **not** collected.
 - **SnippetsFilters Info**a list of directive-context strings from applied SnippetFilters and a total count per strings. The actual value of any NGINX directive is **not** collected.
+- **Control Plane Pod Count** the count of NGINX Gateway Fabric Pods.
+- **Data Plane Pod Count** the count of NGINX data plane Pods.
 This data is used to identify the following information:
 
 - The flavors of Kubernetes environments that are most popular among our users.