Add Java/JNI bindings and CI test job

[JingsongLi]

Enabling Java applications to use MosaicWriter/MosaicReader via Arrow C Data Interface over JNI.

[leaves12138]

Looks good to me.

I reviewed the Java/JNI binding path, including the Arrow C Data import/export flow, native handle lifecycle, Java InputFile/OutputStream bridging, row-group projection/statistics APIs, and the new CI job. The JNI library builds successfully locally, cargo test --workspace passes, and the GitHub java-test, build-and-test, cpp-test, and check jobs are all green for this head commit. The local Java test run was not applicable in my environment because it is still on JDK 8 while the PR correctly configures CI with JDK 11 for Arrow 18.