adds setAllPeersLost to the configMaps subcomponent of tailnet.Conn --- we'll call this when we disconnect from a coordinator so we'll eventually clean up peers if they disconnect while we are retrying the coordinator connection (or we don't succeed in reconnecting to the coordinator).
Adds a nodeUpdater component, which serves a similar role to configMaps, but tracks information from tailscale going out to the coordinator as node updates. This first PR just handles netInfo, subsequent PRs will
handle DERP forced websockets, endpoints, and addresses.
Work in progress on a subcomponent of the Conn which will handle configuring the wireguard engine on changes. I've implemented setAddresses as the simplest case and added unit tests of the reconfiguration loop.
Besides making the code easier to test and understand, the goal is for this component to handle disconnect and loss updates about peers, and thereby, implement the v2 Tailnet API.
Further PRs will handle peer updates, status updates, and net info updates.
Then, after the subcomponent is implemented and tested, I will refactor Conn to use it instead of the current monolithic architecture.
