hubble/testutils: add FakePeerListReporter
hubble/testutils: add FakePeerListReporter

This fake implementation of the PeerLisReporter interface will be useful
to implement unit tests for `pkg/hubble/relay/observer`.

Signed-off-by: Robin Hahling <042b6757f29293f4affc22596084b908e3917891@gw-computing.net>

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