Respect default_bucket_prefix by default for Estimator code_location

**Describe the feature you'd like**
Currently the `code_location` attribute of the Estimator class defaults to using the `output_bucket` parameter [docs link](https://sagemaker.readthedocs.io/en/stable/api/training/estimators.html#sagemaker.estimator.EstimatorBase):

> If not specified, the default code location is ‘s3://output_bucket/job-name/’.

The [Session object also has a parameter](https://sagemaker.readthedocs.io/en/stable/api/utility/session.html#sagemaker.session.Session) `default_bucket_prefix` that can be configured.

Ideally, if
1. The `output_bucket` part of `output_path` is the `default_bucket`
2. `_is_output_path_set_from_default_bucket_and_prefix` is False

Then the default location should respect both the `default_bucket` as well as the `default_bucket_prefix`.

e.g. `s3://default_bucket/default_bucket_prefix/job-name/`

This change would be implemented in [_stage_user_code_in_s3](https://github.com/aws/sagemaker-python-sdk/blob/23109671f6262269ab54cdd9aeb5ebe4ea640d25/src/sagemaker/estimator.py#L1042).

Otherwise, the default behavior creates artifacts at the root of the bucket. This means that default behavior for environments where IAM bucket write access is limited by prefix (i.e. SageMaker Unified Studio) will fail.

**How would this feature be used? Please describe.**
If this behavior is implemented, model code assets would be uploaded by default to a prefix where write access is allowed.

**Describe alternatives you've considered**
Currently `code_location` needs to be manually configured to work in SageMaker Unified Studio. This is poorly documented as part of features like [ModelStep](https://sagemaker.readthedocs.io/en/stable/workflows/pipelines/sagemaker.workflow.pipelines.html#sagemaker.workflow.model_step.ModelStep) where it needs to be configured in `repack_model_step_settings` as the model.register output populates `output_path` by default in a pipeline.

If this change cannot be implemented in code, explicit documentation should be provided about configuring parameters to output code in the SageMaker Unified Studio project prefix.

Commencez dans src/sagemaker/estimator.py, au niveau de _stage_user_code_in_s3, puis examinez la documentation liée d’Estimator et de Session ainsi que les références à ModelStep/repack_model_step_settings. Le travail est terminé lorsque l’emplacement de code par défaut utilise default_bucket_prefix dans les conditions indiquées pour le chemin de sortie, avec une documentation de la configuration si la modification du code n’est pas possible.

Rédigé par le modèle d'indexation à partir du texte de l'issue.