endpoint: Add tests,benchmarks for headerfile write
endpoint: Add tests,benchmarks for headerfile write

Add tests and benchmarks that assist in assessing the cost of writing
endpoint information to a headerfile.

Signed-off-by: Joe Stringer <16a9a54ddf4259952e3c118c763138e83693d7fd@cilium.io>

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