Conscrypt's SSLContext fails when given a SunJSSE TrustManager.

The following tests fails:

```
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.security.KeyManagementException;
import java.security.KeyStore;
import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.security.Provider;
import java.security.SecureRandom;
import java.security.Security;
import java.security.UnrecoverableKeyException;
import java.security.cert.CertificateException;

import javax.net.ssl.HttpsURLConnection;
import javax.net.ssl.KeyManager;
import javax.net.ssl.KeyManagerFactory;
import javax.net.ssl.SSLContext;
import javax.net.ssl.TrustManager;
import javax.net.ssl.TrustManagerFactory;

import org.conscrypt.Conscrypt;
import org.junit.BeforeClass;
import org.junit.Test;

public class TestTLS13 {

@BeforeClass
public static void loadconscrypt() {
Provider p = Conscrypt.newProviderBuilder().build();
Security.insertProviderAt(p, Security.getProviders().length);
}

private void prepare(String trustProvider, String tmftype, String contextProvider) throws NoSuchAlgorithmException, CertificateException, IOException, KeyStoreException, NoSuchProviderException, UnrecoverableKeyException, KeyManagementException {
String javahome = System.getProperty("java.home");
String cacertspath = javahome + "/lib/security/cacerts";

KeyStore ks = KeyStore.getInstance("JKS", "SUN");
ks.load(new FileInputStream(cacertspath), "changeit".toCharArray());

TrustManagerFactory tmf = TrustManagerFactory.getInstance(tmftype, trustProvider);
tmf.init(ks);
TrustManager[] tm = tmf.getTrustManagers();

KeyManagerFactory kmf = KeyManagerFactory.getInstance("NewSunX509", "SunJSSE");
kmf.init(ks, new char[] {});
KeyManager[] km = kmf.getKeyManagers();

SecureRandom sr = SecureRandom.getInstance("NativePRNGNonBlocking");

SSLContext ctxt = SSLContext.getInstance("TLSv1.3", contextProvider);
ctxt.init(km, tm, sr);

URL url = new URL("https://www.google.com");
HttpsURLConnection ctx = (HttpsURLConnection) url.openConnection();
ctx.setSSLSocketFactory(ctxt.getSocketFactory());
InputStream o = (InputStream) ctx.getContent();
o.readAllBytes();
}

@Test
public void testBase() throws NoSuchAlgorithmException, CertificateException, KeyStoreException, NoSuchProviderException, IOException, UnrecoverableKeyException, KeyManagementException {
prepare("SunJSSE", "SunX509", "SunJSSE");
}

@Test
public void testConscrypt() throws NoSuchAlgorithmException, CertificateException, KeyStoreException, NoSuchProviderException, IOException, UnrecoverableKeyException, KeyManagementException {
prepare("Conscrypt", "PKIX", "Conscrypt");
}

@Test
public void testMixed() throws NoSuchAlgorithmException, CertificateException, KeyStoreException, NoSuchProviderException, IOException, UnrecoverableKeyException, KeyManagementException {
prepare("SunJSSE", "SunX509", "Conscrypt");
}
}
```

To be exact, only the testMixed fails, with the exception:
```
javax.net.ssl.SSLHandshakeException: Unknown authType: GENERIC
at org.conscrypt.SSLUtils.toSSLHandshakeException(SSLUtils.java:361)
at org.conscrypt.ConscryptEngine.convertException(ConscryptEngine.java:1138)
at org.conscrypt.ConscryptEngine.readPlaintextData(ConscryptEngine.java:1093)
at org.conscrypt.ConscryptEngine.unwrap(ConscryptEngine.java:880)
at org.conscrypt.ConscryptEngine.unwrap(ConscryptEngine.java:751)
at org.conscrypt.ConscryptEngine.unwrap(ConscryptEngine.java:716)
at org.conscrypt.ConscryptEngineSocket$SSLInputStream.processDataFromSocket(ConscryptEngineSocket.java:833)
at org.conscrypt.ConscryptEngineSocket$SSLInputStream.access$100(ConscryptEngineSocket.java:706)
at org.conscrypt.ConscryptEngineSocket.doHandshake(ConscryptEngineSocket.java:230)
at org.conscrypt.ConscryptEngineSocket.startHandshake(ConscryptEngineSocket.java:209)
at org.conscrypt.ConscryptEngineSocket.waitForHandshake(ConscryptEngineSocket.java:547)
at org.conscrypt.ConscryptEngineSocket.getOutputStream(ConscryptEngineSocket.java:290)
at java.base/sun.net.www.http.HttpClient.openServer(HttpClient.java:499)
at java.base/sun.net.www.http.HttpClient.openServer(HttpClient.java:600)
at java.base/sun.net.www.protocol.https.HttpsClient.(HttpsClient.java:265)
at java.base/sun.net.www.protocol.https.HttpsClient.New(HttpsClient.java:379)
at java.base/sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.getNewHttpClient(AbstractDelegateHttpsURLConnection.java:189)
at java.base/sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1232)
at java.base/sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1120)
at java.base/sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:175)
at java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1653)
at java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1577)
at java.base/java.net.URLConnection.getContent(URLConnection.java:752)
at java.base/sun.net.www.protocol.https.HttpsURLConnectionImpl.getContent(HttpsURLConnectionImpl.java:404)
at fr.jrds.TestTLS13.prepare(TestTLS13.java:60)
at fr.jrds.TestTLS13.testMixed(TestTLS13.java:76)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:567)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)
at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:93)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:40)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:529)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:756)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:452)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:210)
Caused by: java.security.cert.CertificateException: Unknown authType: GENERIC
at java.base/sun.security.validator.EndEntityChecker.checkTLSServer(EndEntityChecker.java:297)
at java.base/sun.security.validator.EndEntityChecker.check(EndEntityChecker.java:152)
at java.base/sun.security.validator.Validator.validate(Validator.java:277)
at java.base/sun.security.ssl.X509TrustManagerImpl.checkTrusted(X509TrustManagerImpl.java:231)
at java.base/sun.security.ssl.X509TrustManagerImpl.checkServerTrusted(X509TrustManagerImpl.java:132)
at org.conscrypt.ConscryptEngineSocket$2.checkServerTrusted(ConscryptEngineSocket.java:156)
at org.conscrypt.Platform.checkServerTrusted(Platform.java:330)
at org.conscrypt.ConscryptEngine.verifyCertificateChain(ConscryptEngine.java:1643)
at org.conscrypt.NativeCrypto.ENGINE_SSL_read_direct(Native Method)
at org.conscrypt.NativeSsl.readDirectByteBuffer(NativeSsl.java:567)
at org.conscrypt.ConscryptEngine.readPlaintextDataDirect(ConscryptEngine.java:1099)
at org.conscrypt.ConscryptEngine.readPlaintextData(ConscryptEngine.java:1083)
... 50 more
```

The problem is a `SSLContext` from the Conscrypt provider is used, with a `TrustManager` from SunJSSE, the default provider used.

But when I explicitly ensure than the `TrustManager` is comming from `SSLContext`, everything is OK.

The problem only arise withe the `SSLContext` is using the `TLSv1.3`. With `TLSv1.2`, everything is fine.

I tested that with Java 16 and Conscrypt 2.5.2.

Is that a bug or a feature ?