fix: GatewayReconciler will fall into a loop and cannot converge to stable state

[potterhe]

What this PR does / why we need it:

GatewayReconciler will determine the change of ListenerStatus to decide whether to update Gateway.status. When Gateway.spec.listeners has many entries (greater than 10 and has a certain relationship with the number of HTTPRoutes), GatewayReconciler will fall into a loop and cannot converge to a stable state (updating status will trigger a new gateway reconciler event, and the new round of reconcile will always find differences). The reason here is that when using reflect.DeepEqual to compare two slice structs, the order of elements will affect the result, and Gateway.status.listeners[].conditions[].lastTransitionTime will always be assigned the current time in each round of reconcile, which should be excluded.

Which issue this PR fixes:

fixes #7031

Special notes for your reviewer:

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• the CHANGELOG.md release notes have been updated to reflect any significant (and particularly user-facing) changes introduced by this PR

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