[AURON #2022] [BUG] Native engine panic on closed channel causes JVM crash.

[slfan1989]

Which issue does this PR close?

Closes #2022

Rationale for this change

When running TPC-DS queries (q60-q69) with Spark 4.0 / JDK 21, the native engine panics when WrappedSender::send attempts to send data into a closed channel. This panic escalates into a JVM crash with exit code 134.

The root cause is a race condition where the producer task continues sending data while the receiver has already been closed/canceled due to task completion or cancellation. The current implementation panics on send failure instead of handling it gracefully.

Link: https://github.com/apache/auron/actions/runs/22128240337/job/63964149831?pr=2018

What changes are included in this PR?

Modified WrappedSender::send in execution_context.rs to gracefully handle channel closure:

• Check send().await.is_err() instead of panicking
• Log debug message with context (partition_id, task_id, session_id) for observability
• Return early without updating metrics when channel is closed

Are there any user-facing changes?

No user-facing changes.
This is an internal fix that prevents JVM crashes when tasks are canceled or completed early.

How was this patch tested?

Exist Junit Test.