feat: support auth account for etcd (#1174)

core/discov/accountregistry.go

@@ -0,0 +1,7 @@
+package discov
+
+import "github.com/tal-tech/go-zero/core/discov/internal"
+
+func RegisterAccount(endpoints []string, user, pass string) {
+	internal.AddAccount(endpoints, user, pass)
+}