Remove namespace restriction for EnvoyProxy parametersRef resource

[arkodg]

Description:

Describe the issue.

Today, we enforce that the EnvoyProxy resource must live in the envoy-gateway-system namespace
https://gateway.envoyproxy.io/v1.0.1/tasks/operations/customize-envoyproxy/

This should be loosened

• Some users may want to keep this config in a different namespace, e.g. knative Add envoy gateway testing knative-extensions/net-gateway-api#738
• This resource will have to live in the same namespace as the Gateway once we support attaching EnvoyProxy to Gatways
  in Support attaching EnvoyProxy resource to Gateways #3317

[optional Relevant Links:]

Any extra documentation required to understand the issue.

[arkodg]

gateway/internal/provider/kubernetes/controller.go

Line 1521 in 3712659

// The EnvoyProxy must be in the same namespace as EG.

needs to be updated to get the namespace from the GatewayClass.Spec.ParamtersRef.Namespace field

[phantooom]

/assign