* [HUDI-1989] Refactor clustering tests for MoR table
* refactor assertion helper
* add CheckedFunction
* SparkClientFunctionalTestHarness.java
* put back original test case
* move testcases out from TestHoodieMergeOnReadTable.java
* add TestHoodieSparkMergeOnReadTableRollback.java
* use SparkClientFunctionalTestHarness
* add tag