appc,ipn/ipnlocal,types/appctype: implement control provided routes

Control can now send down a set of routes along with the domains, and
the routes will be advertised, with any newly overlapped routes being
removed to reduce the size of the routing table.

Fixes tailscale/corp#16833
Signed-off-by: James Tucker <james@tailscale.com>

ipn/ipnlocal/local_test.go

@@ -1169,6 +1169,13 @@ func TestRouteAdvertiser(t *testing.T) {
 	if routes.Len() != 1 || routes.At(0) != testPrefix {
 		t.Fatalf("got routes %v, want %v", routes, []netip.Prefix{testPrefix})
 	}
+
+	must.Do(ra.UnadvertiseRoute(testPrefix))
+
+	routes = b.Prefs().AdvertiseRoutes()
+	if routes.Len() != 0 {
+		t.Fatalf("got routes %v, want none", routes)
+	}
 }
 
 func TestRouterAdvertiserIgnoresContainedRoutes(t *testing.T) {
@@ -1352,6 +1359,17 @@ func (rc *routeCollector) AdvertiseRoute(pfx netip.Prefix) error {
 	return nil
 }
 
+func (rc *routeCollector) UnadvertiseRoute(pfx netip.Prefix) error {
+	routes := rc.routes
+	rc.routes = rc.routes[:0]
+	for _, r := range routes {
+		if r != pfx {
+			rc.routes = append(rc.routes, r)
+		}
+	}
+	return nil
+}
+
 type errorSyspolicyHandler struct {
 	t         *testing.T
 	err       error