Gateway Controller Namespacing

[shaneutt]

Problem Statement

Namespace limitations need to be added to the Gateway controller and all *Route controllers.

Proposed Solution

• implement namespace restrictions in route controllers when --watch-namespaces is in use inside the Gateway and Route controllers
• implement namespace restrictions inside route object validation moved to Gateway Controller Namespacing #2080 as it's a completely separate part of the codebase.

Prerequisites

• Add status updates for HTTPRoute and avoid orphaned data-plane configs #2099
• L7 Gateway API Conformance #2210

Acceptance Criteria

• as a user I should be able to limit the namespaces which a Gateway resource will serve using ALL core options of the namespaces.From spec in Gateway
• backendRefs for HTTPRoute resources need to be namespace restricted according to Gateway namespacing rules also Gateway Controller Namespacing #2080
• as a developer Gateway APIs conformance tests for cross-namespace HTTPRoute tests are configured and passing so when I make contributions I can have confidence I did not break cross namespace restrictions. also Gateway Controller Namespacing #2080

[shaneutt]

Given some conversation that needs to happen upstream (see kubernetes-sigs/gateway-api#977) I'm moving this into the next milestone as we're going to need some time to sort things out upstream, but this doesn't need to block M1.

[rainest]

Split out #2407 and #2408