accesslog: Add DNS.ObservationSource (poller,proxy)
accesslog: Add DNS.ObservationSource (poller,proxy)

We want to emit DNS poll responses as monitor events. They fit well
within the current framework but distinguishing intercepted lookups from
endpoints from DNS polls may be difficult. This change adds an
additional field to explicitly indicate where the DNS information is
sourced from, a DNS Proxy or the DNS poller.

Signed-off-by: Ray Bejjani <7f525154e857f3d57a641a83dddc584f42addc6a@covalent.io>

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