Part 2 changes for test dataset

[Justinyangjy]

PR Type

[Feature]

Short Description

Clickup Ticket(s): Link Clickup Subticket: Link

As detailed in the ticket's subtasks, this branch will focus on subtask2:

Task 2: add test dataset with assumption that the num samples between val and test are different, we split the two metrics and aggregate them separately.

Tests Added

updated test_metrics_reporter_evaluate() in test_basic_client.py, for test dataset metrics.