Integration tests for bdk-ffi

This contains simple tests to make sure bdk-ffi can be used as a dependency for each of the supported bindings languages.

To skip integration tests and only run unit tests use cargo test --lib.

To run all tests including integration tests use CLASSPATH=./tests/jna/jna-5.14.0.jar cargo test.

Before running integration tests you must install the following development tools:

Java and Kotlin, sdkman can help:

sdk install java 11.0.16.1-zulu
sdk install kotlin 1.7.20`