handshake: use new crypto/tls 0-RTT API (#4953)

* handshake: simplify method signature of cryptoSetup.handleEvent

* use the new crypto/tls 0-RTT API

internal/protocol/encryption_level_test.go

@@ -1,6 +1,7 @@
 package protocol
 
 import (
+	"crypto/tls"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -10,6 +11,27 @@ func TestEncryptionLevelNonZeroValue(t *testing.T) {
 	require.NotZero(t, EncryptionInitial*EncryptionHandshake*Encryption0RTT*Encryption1RTT)
 }
 
+func TestEncryptionLevelConversion(t *testing.T) {
+	testCases := []struct {
+		quicLevel EncryptionLevel
+		tlsLevel  tls.QUICEncryptionLevel
+	}{
+		{EncryptionInitial, tls.QUICEncryptionLevelInitial},
+		{EncryptionHandshake, tls.QUICEncryptionLevelHandshake},
+		{Encryption1RTT, tls.QUICEncryptionLevelApplication},
+		{Encryption0RTT, tls.QUICEncryptionLevelEarly},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.quicLevel.String(), func(t *testing.T) {
+			// conversion from QUIC to TLS encryption level
+			require.Equal(t, tc.tlsLevel, tc.quicLevel.ToTLSEncryptionLevel())
+			// conversion from TLS to QUIC encryption level
+			require.Equal(t, tc.quicLevel, FromTLSEncryptionLevel(tc.tlsLevel))
+		})
+	}
+}
+
 func TestEncryptionLevelStringRepresentation(t *testing.T) {
 	require.Equal(t, "Initial", EncryptionInitial.String())
 	require.Equal(t, "Handshake", EncryptionHandshake.String())