feat(java): add OpenTelemetry metrics bridge

[yanghua]

Summary

• Add Java OpenTelemetry metrics support matching pylance’s metrics bridge.
• Expose Lance Rust metrics through JNI with catalog and snapshot APIs.
• Register Java observable instruments for counters, gauges, and histogram bucket/count/sum series.
• Add focused coverage for object-store metrics export through OpenTelemetry.

Tests

• cargo fmt --check
• cargo clippy --all-targets --locked -- -D warnings
• cargo check --manifest-path ./lance-jni/Cargo.toml --locked
• ./mvnw spotless:check
• ./mvnw -Dskip.build.jni=true -DskipTests compile
• ./mvnw -Dtest=org.lance.otel.LanceMetricsTest test

[wjones127]

There's one place I'd like to see a stronger test, but otherwise this looks great!

[lance-gatekeeper]

The bridge closes a real Java observability gap and preserves the process-global recorder and caller-owned MeterProvider contracts. The tested normal lifecycle and histogram semantics work as intended. I did not find a correctness or safety issue that should block this direction.

[yanghua]

@wjones127 Thanks, all comments have been addressed.