Zanzana: periodic sync of team members (#94752)

* Rewrite zanzana collector to fetch all available pages

* Register access control as a background service

* If zanzana is enabled we run Syncs and start Reconciliation job

* Update pkg/services/authz/zanzana/client/client.go

Co-authored-by: Alexander Zobnin <alexanderzobnin@gmail.com>

* Use server lock when doing performing reconciliation

pkg/services/accesscontrol/dualwrite/batch.go

@@ -0,0 +1,19 @@
+package dualwrite
+
+// batch will call fn with a batch of T for specified size.
+func batch[T any](items []T, batchSize int, fn func([]T) error) error {
+	count := len(items)
+	for i := 0; i < count; {
+		end := i + batchSize
+		if end > count {
+			end = count
+		}
+
+		if err := fn(items[i:end]); err != nil {
+			return err
+		}
+
+		i = end
+	}
+	return nil
+}