[SkillCorner V3] Add support for V3 SkillCorner tracking data

[DriesDeprest]

Add support for SkillCorner tracking data version 3 and keeping support for data version 2.

[UnravelSports]

@DriesDeprest I don't think the below generalizes to all versions of JSON.

with open_as_file(raw_data) as raw_data_fp:
        first_line = raw_data_fp.readline().strip()

If I try to load a "structured_data.json" that is stored like below it recognizes only "[" as the first line.

[
    {
        "frame": 0,
        "timestamp": null,
        "period": null,
        "ball_data": {
            "x": null,
            "y": null,
            "z": null,
            "is_detected": null
        },