Switch QUIC client use new ALPS codepoint by default.

GFE has been enabled to support both codepoint more than a year, we should set default to use the new codepoint for QUIC on the client side if there are no explicitly setting.

Chrome side already turned on default to as part of [this change](https://chromiumdash.appspot.com/commit/220d59101b2f05932d29a5c1efb1091019096e4e).

Protected by FLAGS_quic_reloadable_flag_quic_client_default_enable_new_alps_codepoint.

PiperOrigin-RevId: 805503147

quiche/common/quiche_feature_flags_list.h

diff --git a/quiche/common/quiche_feature_flags_list.h b/quiche/common/quiche_feature_flags_list.h
index 1aa4771..bd8cf14 100755
--- a/quiche/common/quiche_feature_flags_list.h
+++ b/quiche/common/quiche_feature_flags_list.h
@@ -20,6 +20,7 @@
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_bbr2_probe_two_rounds, true, true, "When true, the BB2U copt causes BBR2 to wait two rounds with out draining the queue before exiting PROBE_UP and BB2S has the same effect in STARTUP.")
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_bbr2_simplify_inflight_hi, true, true, "When true, the BBHI copt causes QUIC BBRv2 to use a simpler algorithm for raising inflight_hi in PROBE_UP.")
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_block_until_settings_received_copt, true, true, "If enabled and a BSUS connection is received, blocks server connections until SETTINGS frame is received.")
+QUICHE_FLAG(bool, quiche_reloadable_flag_quic_client_default_enable_new_alps_codepoint, false, true, "If true, default-enable quic client to use new ALPS codepoint.")
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_conservative_bursts, false, false, "If true, set burst token to 2 in cwnd bootstrapping experiment.")
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_conservative_cwnd_and_pacing_gains, false, false, "If true, uses conservative cwnd gain and pacing gain when cwnd gets bootstrapped.")
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_default_enable_5rto_blackhole_detection2, true, true, "If true, default-enable 5RTO blachole detection.")

quiche/quic/core/crypto/quic_crypto_client_config.h

diff --git a/quiche/quic/core/crypto/quic_crypto_client_config.h b/quiche/quic/core/crypto/quic_crypto_client_config.h
index f692089..5f89574 100644
--- a/quiche/quic/core/crypto/quic_crypto_client_config.h
+++ b/quiche/quic/core/crypto/quic_crypto_client_config.h
@@ -26,6 +26,7 @@
 #include "quiche/quic/core/quic_time.h"
 #include "quiche/quic/core/quic_types.h"
 #include "quiche/quic/core/quic_versions.h"
+#include "quiche/quic/platform/api/quic_flags.h"
 #include "quiche/common/platform/api/quiche_export.h"
 #include "quiche/common/platform/api/quiche_reference_counted.h"
 
@@ -488,7 +489,8 @@
   bool pad_full_hello_ = true;
 
   // Set whether ALPS uses the new codepoint or not.
-  bool alps_use_new_codepoint_ = false;
+  bool alps_use_new_codepoint_ =
+      GetQuicReloadableFlag(quic_client_default_enable_new_alps_codepoint);
 
   // Configs applied to BoringSSL's SSL object. TLS only.
   QuicSSLConfig ssl_config_;