handlePayload
There are three cases of immediate/scheduled & Partial/Full grading:
Immediate Partial, Scheduled Full
Immediate Full only
Scheduled Full only
When showImmediateScores
is used (true) or it is not yet scheduled grading time (stop collection at) and this is a pipeline-testing grading task, grader will grade in full, otherwise only grade visible test cases (Visibility == Visibility.ALWAYS_VISIBLE).