Write to a separate file instead of updating the same file

[sonalgoyal]

Current perfTestRunner.py updates the testReport. While the information is captured perfectly, we are unable to really see the trend. Current result looks like :

{
    "date": "2025-12-13",
    "time": "00:35:35",
    "test": "febrl_120K",
    "results": {
        "train": 1.51,
        "match": 5.53
    }
}

Instead, if we create a new file named as testName_date_time.csv with columns:

date, time, test, train, match
2025-12-13,00:35:35, febrl_120k, 1.51, 5.53