Implement #633: VTL regular names must be case insensitive

[mla2001]

Summary

Regular names are now case insensitive.

Checklist

• Code quality checks pass (ruff format, ruff check, mypy)
• Tests pass (pytest)
• Documentation updated (if applicable)

[javihern98]

Looks good, thanks! 😊

[javihern98]

Need to handle as well these kind of cases, output component for calc and aggr:

    script = """
        DS_A <- DS_1[calc me_1 := mE_1 * 10];
    """

    data_structures = {
        "datasets": [
            {
                "name": "DS_1",
                "DataStructure": [
                    {"name": "Id_1", "type": "Integer", "role": "Identifier", "nullable": False},
                    {"name": "Me_1", "type": "Number", "role": "Measure", "nullable": True},
                ],
            }
        ]
    }

    data_df = pd.DataFrame({"Id_1": [1, 2, 3], "Me_1": [10, 20, 30]})

    datapoints = {"DS_1": data_df}

    run_result = run(script=script, data_structures=data_structures, datapoints=datapoints)

    print(run_result)