wgengine/wgcfg: plumb down audit log IDs (#5855)

The node and domain audit log IDs are provided in the map response,
but are ultimately going to be used in wgengine since
that's the layer that manages the tstun.Wrapper.

Do the plumbing work to get this field passed down the stack.

Signed-off-by: Joe Tsai <joetsai@digital-static.net>

types/netmap/netmap.go

@@ -76,6 +76,11 @@ type NetworkMap struct {
 	// Domain is the current Tailnet name.
 	Domain string
 
+	// DomainAuditLogID is an audit log ID provided by control and
+	// only populated if the domain opts into data-plane audit logging.
+	// If this is empty, then data-plane audit logging is disabled.
+	DomainAuditLogID string
+
 	UserProfiles map[tailcfg.UserID]tailcfg.UserProfile
 }