re: #14730
Adds support for the workspace updates protocol controller to also program DNS names for each agent.
Right now, we only program names like `myagent.myworkspace.me.coder` and `myworkspace.coder.` (if there is exactly one agent in the workspace). We also want to support `myagent.myworkspace.username.coder.`, but for that we need to update WorkspaceUpdates RPC to also send the workspace owner's username, which will be in a separate PR.