Update JCurl to Java 11

[ldrozdz]

Java 8 has gone to GA in 2014 and, as of 2022, only receives security updates. Additionally, moving to an 11+ version would let us get rid of external dependencies and rely on the JDK only.

@yschimke has kindly contributed a PoC of a Java11 JCurl client:
SymphonyFoundationDevClient.java.txt

The goal of this issue is to improve that code to be API-compatible with the current, Java8-based JCurl.