Gateway controller collisions for cleanup and finalizers

[shaneutt]

Current Behavior

As I found when working on https://github.com/Kong/gateway-operator/pull/1442, it seems possible currently for us to update Gateway resources which we don't control, as we manage cleanup and finalizers for Gateway resources prior to verifying support of those resources via GatewayClass.

Expected Behavior

We should not be updating resources we don't control, as this may collide with other Gateway implementations on the cluster.

Steps To Reproduce

1. deploy the KGO
2. deploy any other Gateway implementation
3. create a Gateway for the other implementation, see that we are adding and removing finalizers to it

Operator Version

c73b6aa

kubectl version

v1.27.10