[SPARK-20461][CORE][SS] Use UninterruptibleThread for Executor and fix the potential hang in CachedKafkaConsumer

## What changes were proposed in this pull request?

This PR changes Executor's threads to `UninterruptibleThread` so that we can use `runUninterruptibly` in `CachedKafkaConsumer`. However, this is just best effort to avoid hanging forever. If the user uses`CachedKafkaConsumer` in another thread (e.g., create a new thread or Future), the potential hang may still happen.

## How was this patch tested?

The new added test.

Author: Shixiong Zhu <shixiong@databricks.com>

Closes #17761 from zsxwing/int.