Remove JNI support and related files

- Deleted the JNI module and all associated files, including callbacks, env, exports, server, and types.
- Updated Cargo.toml to remove the jni dependency and related features.
- Removed JNI-related sections from README.md and CHANGELOG.md.
- Adjusted the GitHub Actions workflow by removing the Rust CI configuration.

src/lib.rs

@@ -55,8 +55,3 @@ pub mod prelude {
         PoolOptions, RateLimitOptions, SchedulerOptions, TargetOptions, TorrentInfo,
     };
 }
-
-#[cfg(feature = "jni")]
-#[path = "../jni/mod.rs"]
-/// JNI entry points consumed by the external JVM bindings.
-pub mod jni_bindings;