chore: Made it easier to use the latest framework version when calling Model.upload_*

[Ark-kun]

Goal: make it easier for the calling functions to ask for the latest framework version.
It turns out that the current approach complicates calling the upload_* functions, because there is no values of the *_version parameter that mean "latest version". This leads to the need to have different code paths depending on whether the user has given an explicit version value.
Example of the problem:

def my_import_xgboost_model(
    model_path: str,
    xgboost_version: Optional[str] = None,
):
    if xgboost_version:
            # Case for when the user has provided explicit version
            aiplatfor.Model.upload_xgboost_model(model_path=model_path, xgboost_version=xgboost_version)
    else:
            # Case for when the user has not provided explicit version
            aiplatfor.Model.upload_xgboost_model(model_path=model_path)

With this small change, the call is simplified:

def my_import_xgboost_model(
    model_path: str,
    xgboost_version: Optional[str] = None,
):
    aiplatfor.Model.upload_xgboost_model(model_path=model_path, xgboost_version=xgboost_version)

P.S. It would be great if the get_prebuilt_prediction_container_uri supported the "latest version" feature.

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Fixes #<issue_number_goes_here> 🦕