Only trigger testing with the platform specified

[llxia]

When the AQA Test Pipeline is triggered by an upstream pipeline at runtime, we only receive the SDK URL for a single platform at a time. We cannot run all platforms specified in the config json file.

We should update the logic. When the config json file is set, by default run all platforms specified in the config json file. If params.PLATFORMS is also set, then only trigger testing for the specified platform.