datapath: add Loader interface
datapath: add Loader interface

This is currently only implemented by `pkg/loader:Loader`.

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

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