## What changes were proposed in this pull request?
https://github.com/apache/spark/pull/21977 added a feature to limit Python worker resource limit.
This PR is kind of a followup of it. It proposes to add a test that checks the actual resource limit set by 'spark.executor.pyspark.memory'.
## How was this patch tested?
Unit tests were added.
Closes#23663 from HyukjinKwon/test_rlimit.
Authored-by: Hyukjin Kwon <gurwls223@apache.org>
Signed-off-by: Hyukjin Kwon <gurwls223@apache.org>