ensure KongClusterPlugin configured as global plugins have the ingress.class annotation

[hbagdi]

KongClusterPlugin can be configured as global plugins using the label global: "true".
KongPlugin can do the same, but that behavior is set to be removed with #681.

Change the store abstraction to only return global plugins if they have a matching ingress.class annotation on them.
This is required to avoid multiple Kong Ingress Controllers from picking global plugins. Users wish to configure different set of global plugins for internal and external ingress controllers.

For more details on background, please see doc in #690.

[rainest]

Handled in #767.

[zffocussss]

what if we have two kong ingress controllers, such as KONG-A and KONG-B.but I want to use a same kongclusterplugin (same plugin code and same plugin conf) in both of the kong ingress controllers?