[SPARK-3595] Respect configured OutputCommitters when calling saveAsHadoopFile

Addresses the issue in https://issues.apache.org/jira/browse/SPARK-3595, namely saveAsHadoopFile hardcoding the OutputCommitter.  This is not ideal when running Spark jobs that write to S3, especially when running them from an EMR cluster where the default OutputCommitter is a DirectOutputCommitter.
It's great that you did this integration test to verify this is working. However, we usually won't merge things like this into the repo because tests that aren't run regularly as part of our harness don't provide much testing value (and often become out of date, etc).

AFAIK the unit test provides pretty good coverage here. Would you mind dropping this from the PR?