types/netmap,*: pass around UserProfiles as views (pointers) instead

Smaller.

Updates tailscale/corp#26058 (@andrew-d noticed during this)

Change-Id: Id33cddd171aaf8f042073b6d3c183b0a746e9931
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

types/netmap/netmap.go

@@ -76,7 +76,9 @@ type NetworkMap struct {
 	// If this is empty, then data-plane audit logging is disabled.
 	DomainAuditLogID string
 
-	UserProfiles map[tailcfg.UserID]tailcfg.UserProfile
+	// UserProfiles contains the profile information of UserIDs referenced
+	// in SelfNode and Peers.
+	UserProfiles map[tailcfg.UserID]tailcfg.UserProfileView
 
 	// MaxKeyDuration describes the MaxKeyDuration setting for the tailnet.
 	MaxKeyDuration time.Duration
@@ -289,7 +291,12 @@ func (nm *NetworkMap) PeerWithStableID(pid tailcfg.StableNodeID) (_ tailcfg.Node
 func (nm *NetworkMap) printConciseHeader(buf *strings.Builder) {
 	fmt.Fprintf(buf, "netmap: self: %v auth=%v",
 		nm.NodeKey.ShortString(), nm.GetMachineStatus())
-	login := nm.UserProfiles[nm.User()].LoginName
+
+	var login string
+	up, ok := nm.UserProfiles[nm.User()]
+	if ok {
+		login = up.LoginName()
+	}
 	if login == "" {
 		if nm.User().IsZero() {
 			login = "?"