pkg/maps/policymap: export PolicyKey type
pkg/maps/policymap: export PolicyKey type

This will allow the PolicyKey type to be used outside of this package.

Signed-off by: Ian Vernon <ian@cilium.io>

tgraf/cilium,eloycoto/cilium,scanf/cilium,michi-covalent/cilium,michi-covalent/cilium,tgraf/cilium,michi-covalent/cilium,tgraf/cilium,cilium/cilium,scanf/cilium,cilium/cilium,tgraf/cilium,tgraf/cilium,michi-covalent/cilium,eloycoto/cilium,scanf/cilium,scanf/cilium,tklauser/cilium,tgraf/cilium,eloycoto/cilium,scanf/cilium,tklauser/cilium,tklauser/cilium,cilium-team/cilium,scanf/cilium,scanf/cilium,eloycoto/cilium,eloycoto/cilium,cilium/cilium,cilium-team/cilium,cilium/cilium,cilium/cilium,tklauser/cilium,tklauser/cilium,eloycoto/cilium,eloycoto/cilium,michi-covalent/cilium