Test that newly-added Java 8 ALPN works

In https://bugs.java.com/bugdatabase/view_bug.do?bug_id=8230977 Java 8 received a backport of the Java 9 ALPN API. It appears to be available starting in 8u251 or u252. Support was added to Netty in https://github.com/netty/netty/pull/10196 and released in 4.1.49.

Since we do some of our own detection, we should make sure it works with these more recent Java 8 versions. Even though Java 8 has very poor AES GCM performance, if it is an additional option it can help users on nicher platforms why may not need high throughput. We will also need to update SECURITY.md.

It may make sense to split out a separate issue for OkHttp.

Start by locating the existing Java ALPN detection and SECURITY.md, then compare the behavior introduced by Java 8u251/8u252 and Netty 4.1.49. Add coverage confirming the newer Java 8 ALPN API is detected and update SECURITY.md as needed; the tests should pass on supported Java versions.

Vom Indexierungsmodell aus dem Issue-Text verfasst.