SHA256withRSA (and more) not supported in Java7ExtendedSSLSession

Using conscrypt-openjdk-uber on non-android java does not support SHA256 client auth certificates.
The error boils down to hardcoded value (see below). Tweaking only this value (e.g. in debugger) to include `SHA256withRSA` makes my certificate working.
`org.conscrypt.Java7ExtendedSSLSession` (and therefor also `org.conscryptJava8ExtendedSSLSession`) hard codes supported algorithms
```
// TODO: use BoringSSL API to actually fetch the real data
private static final String[] PEER_SUPPORTED_SIGNATURE_ALGORITHMS =
new String[] {"SHA1withRSA", "SHA1withECDSA"};
```

My actual usecase is GRPC ok-http client + conscrypt-openjdk-uberjar on oracle jre 8 and openjdk-11. But having the `ExtendedSSLSession.getPeerSupportedSignatureAlgorithms()` returning this limited values (as called by `sun.security.ssl.X509KeyManagerImpl` in all java versions I checked) is the root problem.