Add a RemoteHandshakeService.TlsHandshakeV2 rpc to Alia, and implement it for IETF QUIC.

The design is described in go/split-handshake-v2/edit#heading=h.7gksx9r8ttfj

PiperOrigin-RevId: 355390612
Change-Id: I7edb69f7012568976530cd6fa22e4b46710d8b8c
diff --git a/quic/core/tls_client_handshaker.h b/quic/core/tls_client_handshaker.h
index 71714e2..42d587f 100644
--- a/quic/core/tls_client_handshaker.h
+++ b/quic/core/tls_client_handshaker.h
@@ -81,6 +81,8 @@
 
   void AllowEmptyAlpnForTests() { allow_empty_alpn_for_tests_ = true; }
   void AllowInvalidSNIForTests() { allow_invalid_sni_for_tests_ = true; }
+  SSL* GetSslForTests() { return tls_connection_.ssl(); }
+  const SSL* GetSslForTests() const { return tls_connection_.ssl(); }
 
  protected:
   const TlsConnection* tls_connection() const override {