In QuicConnectionStats, rename max_packet_size to egress_mtu, and max_received_packet_size to ingress_mtu.

Also change the value of egress_mtu from max_packet_size() to long_term_mtu_. The two are identical except when max_packet_size() is temporarily raised for MTU packets.

PiperOrigin-RevId: 374655611
diff --git a/quic/core/quic_connection_stats.h b/quic/core/quic_connection_stats.h
index c2a64ce..570b44e 100644
--- a/quic/core/quic_connection_stats.h
+++ b/quic/core/quic_connection_stats.h
@@ -103,8 +103,10 @@
   int64_t min_rtt_us = 0;  // Minimum RTT in microseconds.
   int64_t srtt_us = 0;     // Smoothed RTT in microseconds.
   int64_t cwnd_bootstrapping_rtt_us = 0;  // RTT used in cwnd_bootstrapping.
-  QuicByteCount max_packet_size = 0;
-  QuicByteCount max_received_packet_size = 0;
+  // The connection's |long_term_mtu_| used for sending packets.
+  QuicByteCount egress_mtu = 0;
+  // Size of the largest packet received from the peer.
+  QuicByteCount ingress_mtu = 0;
   QuicBandwidth estimated_bandwidth = QuicBandwidth::Zero();
 
   // Reordering stats for received packets.