Konnect entities: global plugins

[pmalek]

Problem statement

#370 introduces support for Konnect entities. #438 specifically introduces support for KongPlugin bindings.

This tasks tracks the effort of introducing global plugin support.

Acceptance

• Users can configure global plugins in Konnect through KGO CRDs

[mlavacca]

Global plugin API is tracked in Kong/kubernetes-configuration#7. For the sole context of Konnect, a namespace plugin binding could be leveraged as a global one, but if we consider using such a new resource in KIC as well, we'll likely have to introduce a new cluster-wide resource, as explained in Kong/kubernetes-configuration#7 (comment)