Disable default features in dependencies, especially jni

[Evrey]

JNI heavily lags behind with transitive dependency updates. With default features on it pulls in useless dependencies like windows-sys, resulting in multiple pulled depedency versions. That in turn needlessly lengthens package download and build times, which in turn hurts CI.

[MarijnS95]

We've tried upgrading in #126, but there has not yet been a matching jni 0.22 release for jni-sys 0.4.

Feel free to PR changes that affect default feature flags.