[Java] Add zero-copy ingestIpcBatch for Arrow Flight

[danilonajkov-db]

What changes are proposed in this pull request?

Adds ZerobusArrowStream.ingestIpcBatch(byte[]) — a zero-copy ingestion path that forwards
pre-serialized Arrow IPC bytes directly into the Flight wire format, skipping the
deserialize → re-serialize round-trip performed by ingestBatch(VectorSchemaRoot). Wires
through a new nativeIngestIpcBatch JNI export to ZerobusArrowStream::ingest_ipc_batch
in the Rust core.

Why: the existing ingestBatch path materializes a RecordBatch JNI-side only to
immediately re-encode it for Flight. Callers that already hold IPC bytes (e.g. from Kafka,
files, network sources) had no way to skip this. The new method gives them one.

Constraint: incompatible with streams configured with ipcCompression — raw IPC bytes
wouldn't match the codec. Surfaces as a ZerobusException.

How is this tested?

• mvn test -Dtest=ArrowIntegrationTest against staging — 18 tests pass, including 3 new
  ones for this feature: happy-path ingest, compression-rejection, null/empty input.
• cargo clippy -p zerobus-jni -- -D warnings, cargo fmt --check, cargo test --lib —
  clean.
• mvn spotless:check, full Java unit tests — clean.