[ring_hash] delegate to pick_first as per dualstack design (#34244)

Rolls forward the changes from #33093 and some from #33568, which were
rolled back in #33718.

src/core/BUILD

@@ -4833,16 +4833,18 @@ grpc_cc_library(
     deps = [
         "channel_args",
         "closure",
+        "delegating_helper",
         "error",
-        "grpc_lb_subchannel_list",
+        "grpc_lb_policy_pick_first",
         "grpc_service_config",
         "json",
         "json_args",
         "json_object_loader",
         "lb_policy",
         "lb_policy_factory",
+        "lb_policy_registry",
+        "pollset_set",
         "ref_counted",
-        "subchannel_interface",
         "unique_type_name",
         "validation_errors",
         "//:channel_arg_names",

src/core/lib/resolver/server_address.h

@@ -58,6 +58,7 @@ class ServerAddress {
   ServerAddress& operator=(ServerAddress&& other) noexcept;
 
   bool operator==(const ServerAddress& other) const { return Cmp(other) == 0; }
+  bool operator<(const ServerAddress& other) const { return Cmp(other) < 0; }
 
   int Cmp(const ServerAddress& other) const;
 

test/cpp/end2end/xds/xds_ring_hash_end2end_test.cc

@@ -995,7 +995,7 @@ TEST_P(RingHashTest, ReattemptWhenAllEndpointsUnreachable) {
   CheckRpcSendFailure(
       DEBUG_LOCATION, StatusCode::UNAVAILABLE,
       MakeConnectionFailureRegex(
-          "ring hash cannot find a connected subchannel; first failure: "),
+          "ring hash cannot find a connected endpoint; first failure: "),
       RpcOptions().set_metadata(std::move(metadata)));
   StartBackend(0);
   // Ensure we are actively connecting without any traffic.
@@ -1034,7 +1034,7 @@ TEST_P(RingHashTest, TransientFailureSkipToAvailableReady) {
   CheckRpcSendFailure(
       DEBUG_LOCATION, StatusCode::UNAVAILABLE,
       MakeConnectionFailureRegex(
-          "ring hash cannot find a connected subchannel; first failure: "),
+          "ring hash cannot find a connected endpoint; first failure: "),
       rpc_options);
   gpr_log(GPR_INFO, "=== DONE WITH FIRST RPC ===");
   EXPECT_EQ(GRPC_CHANNEL_TRANSIENT_FAILURE, channel_->GetState(false));
@@ -1070,7 +1070,7 @@ TEST_P(RingHashTest, TransientFailureSkipToAvailableReady) {
   CheckRpcSendFailure(
       DEBUG_LOCATION, StatusCode::UNAVAILABLE,
       MakeConnectionFailureRegex(
-          "ring hash cannot find a connected subchannel; first failure: "),
+          "ring hash cannot find a connected endpoint; first failure: "),
       rpc_options);
   gpr_log(GPR_INFO, "=== STARTING BACKEND 1 ===");
   StartBackend(1);