Overview

Add support of Java integration tests that use classes defining some native methods, load a library implementing them from Java, and test this crate through native methods.

Description

We already have integration tests in Rust thanks to @fpoli, and most things can be tested from Rust using the standard Java library (and it’s usually easier than writing both a Java native method and native code implementing it + a test in Java). However, some things are easier (or only possible) to test from Java — library loading, native methods.