DnsNameResolver SRV and TXT doesn't observe search domains

There's a JDK bug: https://bugs.openjdk.java.net/browse/JDK-8170306 . This was mentioned in #5218.

Since SRV and TXT are still basically experimental, it's unclear how much to prioritize this. It's also unclear how we could solve this. We could use Netty's DNS resolution, although that has its own complexities and risks.