Migrate Kgateway Emitter Features Upstream

[danehans]

Now that #45 has merged, this downstream is aligned with the upstream emitters implementation. This should provide the runway to begin migrating kgateway emitter and Ingress NGINX provider features upstream and deprecate this downstream.

[danehans]

Blocked by #62

[danehans]

Now that #62 has merged, #79 needs to merge upstream for this issue to be unblocked.